"puretuna" is an amalgam of English and Oshivambo, the Oshivambo name "Tunelao" which means loosely "we're fortunate" or "we're blessed" and abbreviated to Tuna, a rather common and genderless handle in Ovamboland, and the english word "pure". So you could interpret puretuna to mean "pure fortune". However, if you are Oshiwambo speaking, you’ll know that while the implied meaning of "tuna" is the same as tunelao, "tuna" by itself really means, "we have". So for the Quaker Oshivambo linguists in the crowd, feel free to interpret it as "we have purity".