grovelyoudaoicibaDictYouDict[grovel 词源字典]
grovel: [16] Old and Middle English had a suffix -ling, used for making adverbs denoting direction or condition. Few survive, and of those that do, most have had their -ling changed to the more logical-sounding -long (headlong and sidelong, for instance, used to be headling and sideling; darkling still hangs on – just – unchanged).

Among them was grovelling, an adverb meaning ‘face downwards’ based on the phrase on grufe ‘on the face or stomach’, which in turn was a partial translation of Old Norse á grúfu, literally ‘on proneness’ (grúfu may be related to English creep). It was not long before grovelling came to be regarded as a present participle, and the new verb grovel was coined from it.
=> creep[grovel etymology, grovel origin, 英语词源]
grovel (v.)youdaoicibaDictYouDict
1590s, Shakespearean back-formation from groveling "on the face, prostrate" (mid-14c.), also used in Middle English as an adjective but probably really an adverb, from gruffe, from Old Norse grufe "prone" + obsolete adverbial suffix -ling (which survives also as the -long in headlong, sidelong). The Old Norse word is found in liggja à grufu "lie face-down," literally "lie on proneness." Old Norse also had grufla "to grovel," grufa "to grovel, cower, crouch down." The whole group is perhaps related to creep (v.). Related: Groveled; grovelled; groveling; grovelling.