The story
- Latin · borrowed from-ica
- English today-ica
From Latin -ica, neuter plural of -icus. Note that etymologically this is not -ic + -a (“(plural ending)”), as -ic is the English form, having dropped the -um, though adding an -a to an English word ending in -ic does produce a superficial etymologically.
Etymology from Wiktionary, CC BY-SA 4.0.