The group of words around grucer and its various and quite numerous derivatives has been discussed by W. Rothwell in "The Legacy of Anglo-French: faux amis in French and English, Zeitschrift für romanische Philologie 109 (1993), 16-46 (pp. 30-31 and n.61). This article is available on the AND site under "Articles on Anglo-Norman topics". The OED derives the verb to grutch from grucer; relevant also are English to grouse and the later to grouch (a later form of grutch). Of grouse, OED notes, rather oddly, "Origin unknown. The word has a curious resemblance to Norman French dialect groucer = Old French groucier, grousser". The entry dates from 1900. The first attestation given for to grouse is 1887.