Etymology

PGmc *umƀi gives OE ymbe ‘around, about (etc.)', next to OIcel umb (later um), OFris umbe (ombe, um(me), om(me)), OS umbi, um, OHG umbi (umpi, umbe), MDu umbe (ombe, um(me), om(me)).  Variants without i-mutation (presumably owing to the word’s frequency in low-stress environments) have been generalized everywhere apart from OE, where the reverse is true.  While it is therefore in principle possible to account for ME spellings implying /u/ as survivals of a native unstressed equivalent to ON umb, the total absence of such a form from the surviving OE corpus makes foreign influence look more attractive, and most authorities adduce at least some ON input. However the ME disyllabic form cannot derive straightforwardly from ON umb, and so may well reflect a blend with OE ymbe (thus TGD, and implied by GDS).  Alternatively, ME umbe can be explained as showing the influence of the verbal prefix umbe-, which has sometimes been understood as in origin a double prefix (um- plus be-); such forms are very common in MDu as well as in older Dan (ombe-), and occur occasionally in MLG (see OED), and it is possible, therefore, that the vocalism of the first syllable of ME umbe might owe something to Dutch as well as, or instead of, ON.  

PGmc Ancestor

*umƀi 

Proposed ON Etymon (OIcel representative)

umb 'around'
(ONP um (1) (præp.))

Other Scandinavian Reflexes

Far um, Icel um, Norw um, Dan om, Sw om

OE Cognate

ymbe ‘around, about (etc.)'

Phonological and morphological markers

[

absence of i-mutation

] (may not be applicable)

Summary category

CC2ac

Attestation

The majority of MED’s citations of the prep. (in its various forms) are from 12c. and early 13c. texts and the bulk of their spellings either indicate direct descent from OE ymb(e) or are found in dial orthographies where <u> can represent /y/ < OE /y/ (e.g. the AB language, LB; see further Dance 2003: 407); the main exceptions are Orrm’s <umbe, ummbenn>.  By the later 14c. the word (in the forms <vmb(e), vmben>) is confined to N and E alliterative poetry (incl. WA and DT). 

Occurrences in the Gersum Corpus

Gaw 589, 1830, 2034; Cl 879, 1384, 1474 etc.; Pat 301, 381; WA 1154, *3250

Also common as a verbal prefix, viz. Gaw vmbe-clypped ‘encompassed, surrounded’ (616), vmbe-foldes ‘enfolds’ (181), vmbe-kesten (see kest), vmbe-lappez ‘enfolds, overlaps’ (628), vmbe-teʒe ‘surrounded’ (770), vmbe-torne, vmbe-weued ‘enveloped’ (581) and Pe vmbegon 'lying around, encompassing' (210), vmbepyʒte 'arrayed round about, adorned' (1052). TPD insert an instance at 3250, emending MS A vp.

Bibliography

MED umbe (prep.) , OED umbe (prep. and adv.)[http://www.oed.com/view/Entry/208754?isAdvanced=false&result=1&rskey=6aHumq&, umbe- (prefix), Dance vmbe, Bj. 224, de Vries um, Mag. um (1), Bj-L. om, Orel *umƀi, Kroonen *umbi-, AEW ymb(e)