a combination of -able and -ity, found on nouns corresponding to adjectives in -able:
capability.
Origin
Middle English-abilite ≪ Latin-ābilitās
Word Origin and History for -ability
word-forming element expressing ability, fitness, or capacity, from Latin -abilitas, forming nouns from adjectives ending in -abilis (see -able). Not etymologically related to ability, though popularly connected with it.