Meaning

adjective capable of being changed or altered in some characteristic

adjective (of the punishment ordered by a court) capable of being changed to one less severe

originEtymology tree English alter Proto-Indo-European *-tḗr Proto-Indo-European *-dʰlom Proto-Indo-European *-dʰlis Proto-Italic *-ðlis Latin -bilis Latin -ābilis Old French -ablebor. Middle English -able English -able English alterable From alter + -able.

Etymology from Wiktionary, CC BY-SA 3.0