mid-15c., from sparing, attested from late 14c. as a present-participle adjective from spare (v.), + -ly (2).
Entries linking to sparingly
spare v.
Old English sparian "to refrain from harming, be indulgent to, allow to go free; use sparingly," from the source of Old English spær "sparing, frugal," from Proto-Germanic *sparaz (source also of Old Saxon sparon, Old Frisian sparia, Old Norse spara, Dutch sparen, Old High German sparon, German sparen "to spare"). Meaning "to dispense from one's own stock, give or yield up," is recorded from early 13c. Related: Spared; sparing.
-ly 2
common adverbial suffix, forming from adjectives adverbs signifying "in a manner denoted by" the adjective, Middle English, from Old English -lice, from Proto-Germanic *-liko- (cognates: Old Frisian -like, Old Saxon -liko, Dutch -lijk, Old High German -licho, German -lich, Old Norse -liga, Gothic -leiko); see -ly (1). Cognate with lich, and identical with like (adj.).
Weekley notes as "curious" that Germanic uses a word essentially meaning "body" for the adverbial formation, while Romanic uses one meaning "mind" (as in French constamment from Latin constanti mente). The modern English form emerged in late Middle English, probably from influence of Old Norse -liga.