A male name. Old German Willahelm, compound of vilja ‘will’ and helma ‘helmet’. It became Guilieim and then Guillaume in French, and was introduced into England by the Normans in the 11th C, from which time it has held its place as one of the commonest men’s names (from the 16th to 19th C, for instance, it averages 20 per cent. of baptismal entries in parish registers), tying with John for first place. The usual abbreviation was Will. There is no direct evidence of the use of Bill in the Middle Ages as a nickname for William (the surnames Bill, Bilson may be from Old English Bil). There are many surnames derived from William and its diminutive, e.g. William, Williams, Williamson, Wilson, Willcock, Wilcox, Wilcoxson, Wilmot (from the common diminutive William-ot), Wilkin,Wilkins, Wilkinson, Wilks, Wilkes, Wilkie, &c. (from the pet-form Wil-kin), Willis, Willet, Willins, Willings. Gill, Gillot, Gillet, &c., are sometimes from Old French Guille, an abbreviation for Guillaume, but may also be from the girl’s name Gill (see Julian). Wilmot was often a girl’s name.

Willelm Regesta Regum Anglo-Normannorum c. 1067. Willelmus Domesday Book 1086, Curia Regis Rolls 1199-1220. Wilecoc Hundred Rolls 1273. Wylymot Poll Tax of West Riding of Yorkshire 1379 1379. Gillet, Gillot, Gillotin, Gilliame, Guillot Exchequer Rolls 1306. Wyll Cocke Lorelle's Bote c. 1515. Gilow, Gylaw Poll Tax of West Riding of Yorkshire 1379 1379. Gilmyn Poll Tax of West Riding of Yorkshire 1379 1379.

The Will is Teutonic for ‘resolution’ (cf. Wilfred); -iam probably represents Teutonic helm, ‘helmet’: therefore, the whole represents either ‘a stout helmet’ or ‘helmet of resolution’ (cf. ‘garment of, robed in, righteousness’), and the name was apparently Ger.—as, of course, it still is in the form Wilhelm—before it spread to all the other European countries. In England it is almost as popular now as ever it was, its most glorious period being from 1066 to ca. 1300; it graces a palace or a mansion as comfortably as it does a semi-detached house or a hovel. It is the second commonest of all ‘Christians’ in England, only John beating it, though Thomas must run it very close. (In slang, a ‘William’ is a bill of exchange.)

A name corrupted from the Old German name Wilhelm, Willihelm, which Wachter derives from weil-helm, protector of rest, defender of tranquillity; I say from vil-helm, strong protector. The nicknames are Will, Willy, Bill, Billy. Mailliw, which is found as a female name, is said to be William spelt backwards.

Teutonic (masculine) - Helmet, or helm, of many.

A Teutonic name, meaning: Helmet of resolve, signifying reso­lute warrior: protector: defender.

A Gaelic name: Uilleam, Middle Gaelic William (1467 MS.); the Gaelic is borrowed from the Eng., Old English Willelm, German Wilhelm, “helmet of resolution” (from will and helm). Hence Mac-william.