Names begining with " St. " are listed under the first
letter following the prefix
e.g. St.Clair is under "C", St.Paul under "P", etc.
| Family Name | Gaelic Equivalent | Original language | English Translation |
| Smith | Mac Gabann | Tenebras expellit et hostes. | He drives forth the darkness and the foe. |
| Smyth | - | Exaltabit honore. | It will exalt with honour. |
| Somers | Ó Somacáin | Prodesse quam conspici. | To do good rather than be conspicuous. |
| Spence | - | Constantia et dillengentia. | By perseverance and diligence. |
| Spillane | Ó Sealáin | Pro Deo et patria. | For God and country. |
| Stack | Stac | Virtute et valore. | By virtue and valour. |
| Stafford | Stafort | Virtus basis vitae. | Virtue is the basis of life. |
| Stanley | De Stainléig | Sans changer. | Without changing. |
| Stapleton | Mac An Gaill | Vide sed cui vide. | Trust but in whom take care. |
| Staunton | Mac An Mile | Semper vigilans. | Always watchful. |
| Steele | - | Absque labore nihil. | Nothing without labour. |
| Stephens | Mac Stiofáin | Carpe diem. | Seize the present opportunity |
| Stevenson | Mac Stiofáin | Coelum non solum. | Heaven not earth. |
| Stewart | Stiobard | Nil desperandum est. | We must never despair. |
| Stokes | Stóc | Vincit omnia pertinax virtus. | Stubborn virtue conquers all. |
| O'Sullivan | Ó Suilleabain | Lám foisteanac abú. | The constant hand defying. |
| Sutton | De Sutún | Fide et fortitudine. | With faith and fortitude. |
| Swan | Mac Suain | Spero meliora. | I hope for better things. |
| Smallman | - | - | My word is my bond. |
| Smit | - | Nil desperandum. | Never dispair. |
| Smith | - | - | Hold fast. |
| Smith | - | - | Ready. |
| Smith | - | En Dieu est mon espoir. | In God is my hope. |
| Smith | - | Pro rege et patria. | For king and country. |
| Smith | - | Semper fidelis. | Always faithful. |
| Smith | - | Tu ne cede malis. | Yield not to misfortunes. |
| Smyth | - | Vincit veritas. | Truth conquers. |
| Soltau | - | Miseris succurrere disco. | I learn to succour the unfortunate. |
| Somerville | - | - | Fear God in life. |
| Somerville | - | - | Hold fast. |
| Spaight | - | Vi et virtute. | By strength and valour. |
| Spange | - | Fata viam invenient. | Fates will find the way. |
| Sparrow | - | Spero. | I hope. |
| Spearman | - | Dum spiro spero. | While I breath I hope. |
| Speid | - | - | Speed well. |
| Spence | - | - | Fear God only. |
| Spry | - | Dum spiro spero. | While I breath I hope. |
| Stachan | - | - | Forward. |
| Stacpoole | - | - | I die for those I love. |
| Stacpoole | - | Pro Deo et pro patria. | For God and for country. |
| Stalybridge | - | Absque labore nihil. Nothing without labour. Nothing without labour. | - |
| Stamer | - | Virtute et valore. | By virtue and valour. |
| Stancomb | - | - | Do right, fear not. |
| Stanhope | - | A deo et rege. For God and king. For God and king. | - |
| Stanhope | - | In hoc signo vinces. | Under this sign you shall conquer. |
| Stanley | - | Frangas non flectes. | You may break, but shall not bend me. |
| Stansford | - | Nosce teipsum. | Know thyself. |
| Stapleton | - | Fide sed cui vide. | Trust, but be careful whom (you trust). |
| Stapylton | - | Fide sed cui vide. | Trust, but be careful whom (you trust). |
| Staunton | - | Dum spiro spero. | While I breath I hope. |
| Staveley | - | Fidelis ad urnam. | Faithful to the tomb. |
| Stawell | - | Vigilanter. | Watchfully. |
| Steavenson | - | Coelum non solum. | Heaven not earth. |
| Steel | - | - | Steel to the back. |
| Steele | - | Semper fidelis. | Always faithful. |
| Stenhouse | - | Fortis et fidelis. | Brave and faithful. |
| Stephens | - | Vigilans et audax. | Vigilant and bold. |
| Steuart | - | - | Firm. |
| Steuart | - | - | My hope is constant in thee. |
| Steuart | - | Semper fidelis. | Always faithful. |
| Stewart | - | - | Forward. |
| Stewart | - | - | I mean well. |
| Stewart | - | - | Pass forward. |
| Stewart | - | - | Resolve is power. |
| Stewart | - | Omne solum forti patria. | Every sail to a brave man in his country first. |
| Stewart | - | Pro rege et patria. | For king and country. |
| Stewart | - | Spero meliora. | I hope for better things. |
| Stewart | - | Virtutis praemium. | Virtues reward. |
| Stibbert | - | Per ardua. | Through difficulties. |
| Stieglitz | - | Spec mea in Deo. | God is my hope. |
| Stilwell | - | - | Hold fast. |
| Stirling | - | - | By wounding I cure. |
| Stirling | - | - | For right. |
| Stirling | - | - | Gang forward. |
| Stirling | - | - | I renew my age. |
| Stirling | - | Semper fidelis. | Always faithful. |
| Stocker | - | Non sibi sed toti. | Not for one self but for all. |
| Stone | - | Nil desperandum. | Never dispair. |
| Stone | - | Vive ut vivas. | Live that you may live forever. |
| Stoney | - | Nunquam non paratus. | Never unprepared. |
| Stopford | - | Patriae inflici fidelis. | Faithful to my unhappy country. |
| Storer | - | Dum spiro spero. | While I breath I hope. |
| Strachey | - | Coelum non animum. | Climate may change, but not the character. |
| Strange | - | Fortes fortuna juvat. | Fortune favours the bold. |
| Strangways | - | Faire sans dire. | To do without speaking. (Deeds not words.) |
| Strode | - | Malo mori quam foedari. | Death rather than dishonour. |
| Stuart | - | - | Forward. |
| Stuart | - | Semper paratus. | Always prepared. |
| Stuart | - | Virtute. | By virtue. |
| Studdy | - | Fide sed cui vide. | Trust, but be careful whom (you trust). |
| Sturges | - | Esse quam videri. | To be, rather than to seem. |
| Sturgis | - | Esse quam videri. | To be, rather than to seem. |
| Sturt | - | En Dieu est tout. | In God is all. |
| Styles | - | Perge sed caute. | Advance but cautiously. |
| Le Sueur | - | - | Sure. |
| Surman | - | - | Yet in my flesh shall I see God. |
| Surtees | - | Malo mori quam foedari. | Death rather than dishonour. |
| Sutherland | - | - | Butt sicker. |
| Sutherland | - | - | Still without fear. |
| Suttie | - | - | Nothing hazard, nothing have. |
| Sutton | - | Fidelis usque ad mortem. | Faithful even to death. |
| Sutton | - | Toujours prest | Always nimble. |
| Swan | - | Fidelitas vincit. | Faithfulness conquers. |
| Swann | - | Fideliter. | Faithfully. |
| Mac Swean | - | - | By the providence of God. |
| Swift | - | Festina lente. | Be quick without impetuosity. |
| Swire | - | Esse quam videri. | To be, rather than to seem. |
| Swyne | - | Esse quam videri. | To be, rather than to seem. |
| Symonds | - | Dum spiro spero. | While I breath I hope. |
| Symons | - | Fuimus. | We have been. (We have made our mark.) |
| Synge | - | Non sibi sed toti. | Not for one self but for all. |
| Synnott | - | Sine macula. | Without stain. |
| Sources: | |
| Irish Family Mottoes | "The General Armory of England, Scotland, Ireland, and Wales." |
| By Tomás ó Baoill | by Sir John Bernard Burke |