u-mutation.
This specially Northern mutation, which appears far later than the i-mutation, is also to be found in Shetland Norn, but is difficult to substantiate, as a has generally changed to o. Such an o, long or short, proceeding from an original a in the stem of feminine words ending in -a, can stand partly as a u-mutation of a, partly as a regular Shetlandic development of a.
In Færoese, the u-mutation from the accusative, genitive and dative in -u has generally entered into the nominative in -a, e.g. fjøra, gøla, søga, blonda (O.N. fjara, gala, saga, blanda), in No. in most cases also, e.g. fjøra, “soga (søga)” from “saga”, “blanda”, blended drink, whey and water, has, in single No. dialects, the mutated parallel-form blonda (cf. Fær. blönda), but in Shetl. the word is bland, without mutation. On account of its meaning, it cannot be the neuter word “bland”, but must be No., Fær. and Icel. blanda, f.).
Without mutation: mara, sb., mud (= Fær. marra, f.) and mara, sb., night-mare, O.N. mara, f. Also mera in Shetl.
Shetl. (Fo.) fjora [fjora, fjɔra] (prop. foreshore, ebb, now with somewhat altered meaning, see the Dictionary), may be a form with u-mutation such as No. and Fær. fjøra (O.N. fjara, acc. fjǫru), but not necessarily.
Shetl. Baga (a cow with a back of a certain colour), Starabaga, *baka, f., from bak, back, has no u-mutation.
On the other hand, the u-mutation is doubtless to be found in bjoget (long o), *boget, adj., applied to an animal with a back of a certain colour, *bǫkóttr from bak. In a similar manner moget [mōgət]: with a belly of a certain colour, *mǫgóttr from magi (belly), in which the relation is more obscure, because also the word “magi” in Shetl. has become an o: mogi.
blogaben: "blǫkubein (from O.N. blaka, f.).
blokka, blokk: O.N. *blaðka.
bonga, sb.: *banga, f.
longa-fish (O.N. langa, Fær. longa).
ronga, sb., wrong: *ranga, f.
*skjoldra: *skjaldra, f.
On the other hand, the ø-sound in føger [føgər] (Ub.), sun (tabu-name), indicates that this word is the mutated form fǫgr, f., from fagr, adj. Also [fȯgər, fɛgər, fɛg] (Un., Yn.). “fȯgər”, like “føgər”, originates doubtless from “fǫgr”.
As the accusative, genitive and dative forms ending in -u, from feminine words ending in -a, have generally been dropped in Shetlandic, and, with some few exceptions, only the nominative forms ending in -a are preserved, alternating with forms without endings (generally through the dropping of -a), or sometimes with the ending -i for an older -a, and as mutation in the nominative forms is irregular, it must remain doubtful, in most cases, how far the -o from an original -a, in such words, is due to u-mutation or not in Shetlandic.
