suffix expressing ability or capacity, from L. -abilitas, forming nouns from adjs. ending in -abilis (see able). Not etymologically related to ability, though popularly connected with it.
suffix expressing ability, capacity, fitness, from L. -ibilis, -abilis, forming adjectives from verbs, from PIE *tro-, a suffix used to form nouns of instrument. In L., infinitives in -are took -abilis, others -ibilis; in Eng., able is used for native words, -ible for words of obvious L. origin. The Latin suffix is not etymologically connected with able, but it long has been popularly associated with it, and this has contributed to its survival...