O.E. cræft "power, strength, might," from P.Gmc. *krab-/*kraf-. Sense shifted to "skill, art" (via a notion of "mental power"), which led to the n. meaning of "trade." Use for "small boat" is first recorded 1671, probably from some nautical sense of "vessels of small craft," referring either to the trade they did or the seamanship they required.