Words related to -able
mid-15c. (late 12c. as a surname), a variation or alteration of Middle English rother, from Old English roðor "paddle, oar," from Proto-Germanic *rothru- (source also of Old Frisian roðer, Middle Low German roder, Middle Dutch roeder, Dutch roer, Old High German ruodar, German Ruder "oar"), from *ro- "steer" (from PIE root *ere- "to row") + suffix *-þra, used to form neutral names of tools.
The original sense is obsolete. The meaning "broad, flat piece of wood attached to the stern of a boat and guided by a tiller for use in steering" is from c. 1300. For shift of -th- to -d- compare burden (n.1), murder (n.); simultaneous but opposite movement turned -d- to -th- in father (n.), etc.
Middle English sadel, from Old English sadol "contrivance secured to the back of a horse, etc., as a seat for a rider," from Proto-Germanic *sathulaz (source also of Old Norse söðull, Old Frisian sadel, Dutch zadel, zaal, German Sattel "saddle"), from PIE root *sed- (1) "to sit" + Germanic suffix *-þra, used to form neutral names of tools.
Extended to various things resembling or functioning as a saddle. Figurative phrase in the saddle "in an active position of management" is attested from 1650s. Saddle-horse "horse for riding" is from 1660s. Saddle-stitch (n.) is from bookbinding (1887).
"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]