able (adj.)

"having sufficient power or means," early 14c., from Old French (h)able "capable; fitting, suitable; agile, nimble" (14c.), from Latin habilem, habilis "easily handled, apt," verbal adjective from habere "to hold" (from PIE root *ghabh- "to give or receive").

"Easy to be held," hence "fit for a purpose." The silent h- was dropped in English and resisted academic attempts to restore it 16c.-17c. (see H), but some derivatives (such as habiliment, habilitate) acquired it via French. Able seaman, one able to do any sort of work required on a ship, may be the origin of this:

Able-whackets - A popular sea-game with cards, in which the loser is beaten over the palms of the hands with a handkerchief tightly twisted like a rope. Very popular with horny-fisted sailors. [Smyth, "Sailor's Word-Book," 1867]

Definitions of able

able (adj.)
(usually followed by `to') having the necessary means or skill or know-how or authority to do something;
able to get a grant for the project
she was able to program her computer
able to swim
we were at last able to buy a car
able (adj.)
have the skills and qualifications to do things well;
able teachers
Synonyms: capable
able (adj.)
having inherent physical or mental ability or capacity;
human beings are able to walk on two feet
able to learn
Superman is able to leap tall buildings
able (adj.)
having a strong healthy body;
every able-bodied young man served in the army
an able seaman
Synonyms: able-bodied