n. [A. S. bäc], Lat. tergum, back, Eg. 218, Edda 29, 30, Hkr. i. 337: in metaph. phrases, bera sök á baki, to be guilty, Gþl. 539; leggja bleyðiorð á bak e-m, to load, charge one with being a coward. Fas. ii. 530; hafa mörg ár á baki, to ‘carry a weight of years’ Ísl. ii. 456: of horseback, léttr á baki, Sturl. ii. 195; fara á bak, to mount; stíga af baki, to dismount, Eg. 397, Grág. ii. 95: in other relations, as adv., at hurðar-baki, behind the door; at húsa-baki, at the back of the houses; að fjalla-baki, behind the mountains; handar-bak, the back of the hand.

2. á bak or á baki used as a prep. or as an adv.; á bak (acc.) if denoting motion, á baki (dat.) if without motion:

α. loc. behind, at the back of; á baki húsunum, Háv. 49, Nj. 28; at baki þeim, at their back, Eg. 91, Nj. 261, 262, 84, Eg. 583; Hrútr kveðst þat ætla, at hans skyldi lítt á bak at leita, he should not be found in the rear, Ld. 278; berr á baki, unbacked, helpless, in the proverb, Nj. 265, Grett. 154: metaph., ganga á bak e-u, orðum, heitum …, to elude, evade one’s pledged word, Fms. ii. 209, Ísl. ii. 382; göra e-t á baki e-m, in one’s absence, behind one’s back, N. G. L. i. 20; á bak aptr (= aptr á bak), backward; falla; á b. a., Eb. 240, Nj. 9, Eg. 397, Háv. 48 new Ed.; til baks, better til baka, to back, Sturl. ii. 203; brjóta á bak, prop. to break one’s back, Fms. viii. 119; to break, subdue, and also to make void, annul; brjóta á bak Rómverja, to ‘break the back’ of the R., defeat them, 625. 65; Heiðrekr vildi öll rúð fóður síns á bak brjóta, Fas. i. 528.

β. temp. with dat. past, after; á bak Jólum, after Yule, Fms. viii. 60; á b. Jónsvöku, ix. 7: metaph., Héðinn kvaðst eigi hirða hvat er á bak kæmi, H. said he did not care for what came after, Fas. i. 402; muntú eigi vera mót Njáli, hvat sem á b. kemr, Nj. 193.