A prefix in some forty words formed in ME, chiefly transitive verbs but with a smattering of participles and gerunds and one noun. The prefix has three main senses: (1) the primary sense of ‘surrounding, encircling, in a circle, around’ (e.g., the verbs umcasten, umclippen, umclosen, umlouken (b), umsegen, umsitten, umyede; the gerunds umganginge and umstandinge; and the noun umgang(e); (2) the related sense of ‘enveloping, wrapping, clothing, covering’ (e.g., the verbs umclethen, umfolden (a), umhilen, umloken v.(1), umshaden, umshadwen, umwrithen; and the gerund umshadwinge); and (3) the extended sense of ‘about, concerning, with regard to’ (e.g., the verbs umloken v.(2), umsen, umthinken). Frequently the nonprefixed forms of the words in question already have these senses, and in such cases the prefix may be considered merely reinforcing or redundant. The prefix may also appear in another eighteen verbs and one participle possibly derived from words beginning with bi-, but the evidence is ambiguous because these words could also be derived from umb(e)- pref. and the non-bi- forms. The words in question are: the verbs umbecasten, umbeclappen, umbeclippen v.(1), umbeclosen, umbedelven, umbefolden, umbegon, umbegrippen, umbelappen, umbeleien, umbeloken, umberouen, umbesegen, umbesen, umbeshadwen, umbespreden, umbestriden, umbethinken; and the participle umbegrouen. The texts containing the unambiguous occurrences of um- are chiefly N, and almost exclusively N and NM, and, although only one of the words involved may be derived directly from ON (umgang(e n.), this dialectal configuration confirms the probable ON origin of the prefix. Similarly, in the nineteen ambiguous words it is likely that most of the N and NM examples are from um- plus the bi- form rather than from umb(e)- plus the non-bi- form. The prefix is used almost exclusively with words of Gmc. (usu. OE) origin; only the verbs umbracen, umclosen, and umsegen and the participle umtiffed are of non-Gmc. (specifically OF) origin, and the three verbs have ME counterparts in em- or en- (embracen, enclosen, ensegen) which may have had an influence in their creation. Many of the um- words have counterparts in umb(e)-; all of these have been noted with cross-references in the relevant entries.