The story
From similar + -ly, with nonetymological -i- perhaps due to influence from adverbs derived from adjectives ending in -ary, e.g. necessarily, primarily, and ordinarily.
Etymology from Wiktionary, CC BY-SA 4.0.
From similar + -ly, with nonetymological -i- perhaps due to influence from adverbs derived from adjectives ending in -ary, e.g. necessarily, primarily, and ordinarily.
Etymology from Wiktionary, CC BY-SA 4.0.