Slithy = lithe and slimey (according the Dodgson himself)
Gyre = See Yeats, "...the widening gyre..."
Gimbel = a mounting for compasses, etc. which keeps them level
Dottle = the unburned tobacco left in a pipe
Raths = old bronze age fortified farms(from the Irish)
Momey = variant of "Mommy," a child's term for mother
Vorpal = a type of steel, similar to damascus, formerly used in fencing foils and seaxs.
Mimsy or Mimsey = a delicate silken fabric; hence, anything similar
Toves = var. of British 19th Century slang word "Cove": e.g. "flash cove"