Bulbasaur: Has a bulb on its back and is a dinosaur
Ivysaur: Plant on its back is poison ivy and is a dinosaur
Venusaur: Has a venus fly trap on its back and is a dinosaur
Charmander: Char as in charcoal and is a salamander
Charmeleon: Char as in charcoal and is a chameleon
Charizard: Char as in charcoal, it's a lizard
Squirtle: Squirt means water, tail is like a squirrel's tail, and is a turtle
Wartortle: The marks on it's face is like the ones on Indians when there was a war and is a turtle
Blastoise: Is a tortoise
Caterpie: Is a caterpillar
Metapod: Meta as in metaphase (middle phase), pod as in a pod for evolution
Butterfree: Is a butterfly that's free
Kakuna: Is a cocoon
Beedrill: Is a bee and has a stinger that looks like a drill
Pidgey: Is a pidgeon
Spearow: Is a sparrow
Ekans: Snake spelled backwards
Arbok: Cobra spelled with a K spelled backwards
Pikachu: A pika is an animal that is mouselike
Raichu: Rai like "ray" of light
Ninetales: Has nine tails
Venonat: Veno means poison and is a gnat
Venomoth: Venom means poison and is a moth
Diglett: Is a mole that digs
Dugtrio:
A digging trio
Meowth: Cats usually meow
Persian: Persian is a type of cat
Geodude: Geo means earth, Geode is a type of rock
Graveler: Gravel means rock or ground
Golem: A Golem is a construction machine with short legs and long arms
Mankey: Is a monkey
Primeape: Is an ape
Ponyta: Is a pony
Rapidash: Has a rapid dash
Slowpoke: Is a slowpoke
Slowbro: The shell on its tail is its "bro"
Magnemite: Is a magnet
Magneton: Is a magnet
Doduo: Is a dodo (kind of bird) and is a duo (group of 2)
Dodrio: Is a dodo and is a trio
Seel: Is a seal
Dewgong: A dugong spelled with dew instead of du
Grimer: Grime means dirt or mess
Shellder: Is chowder
Cloyster: Is a clammed oyster
Haunter: Likes to haunt
Onix: Onyx means a piece of quartz that's grayish
Drowzee: Makes people drowzy
Hypno: Has hypnotic powers
Krabby: Is a crab
Voltorb: Volt means electric and orb means ball
Electrode: Electrode is a measurement of voltage
Exeggcute: Sounds like execute with egg in it
Exeggcutor: Executor with egg in it
Cubone: Has bone in it
Marowak: Marrow is a part of the bone
Hitmonlee
: Lee as in Bruce Lee
Hitmonchan
: Chan as in Jackie Chan
Lickitung
: It licks a lot with its tongue
Rhyhorn
: Is a rhino and has a horn
Rhydon
: Is a rhino
Tangela
: Is a big tangle
Kangaskahn
: Is a kangaroo
Horsea
: Seahorse mixed up
Seadra
: Lives in the sea
Staryu
: Is a star
Starmie
: Is a star
Mr.Mime
: Is a mime
Scyther
: A scythe is a type of blade
Electabuzz: Elect means electric
Magmar: Magma is in its name
Pinsir: Is a pincher
Tauros: Taurus is a bull constellation
Magikarp: Carp is a type of fish
Ditto: Ditto means a copy of something
Vaporeon
: Vapor sort of means water
Jolteon
: Jolt sort of means electric
Flareon
: Flare sort of means fire
Porygon
: Is a polygon
Omanyte
: Omanite is a rock with a spiral on it
Omastar: Is an omanite and is a star
Aerodactyl
: Is a pterodactyl
Snorlax
: Likes to snore and relax
Articuno
: Artic meaning ice and uno is one in Spanish
Zapdos: Zap meaning electric and dos is two in Spanish
Moltres: Mol meaning fire and tres is three in Spanish
Dratini: Is a tiny dragon
Dragonaire: "Aire" as in "heir to the throne" to Dragonite
Dragonite:
A Dragon knight
Mewtwo
: A clone of Mew
Mew
: Sometimes cats make a mew sound
Thanks to J. Murray and Donphan611 for sending some origins