From Middle Englishstarkli, starcliche, sterkliche, stercliche, from Old Englishstearclīċe(“strongly; stoutly; vigorously; vehemently; fiercely; strictly”), from Proto-Germanic*starkulīka(“strongly; stiffly”), from *starkulīkaz(“strong; rigid”), from *starkuz(“strong; stiff; stark”), equivalent to stark +-ly.