Etymology

cp. OIcel þó ‘though, yet’ < VAN *þōh < PGmc *þauh (< *þat + *uxwē), showing typical ON development of /ɑu/ before /x/; cp. OE þēah, Go þauh, OFris thāh, doch, OS thōh, OHG doh. For differing earlier views, see Bj. 73–4.

PGmc Ancestor

*þauh 

Proposed ON Etymon (OIcel representative)

þó ‘though, yet’ 
(ONP þó (adv.))

Other Scandinavian Reflexes

Far tó, Icel þó, Norw do, da, ODan do, thoo, OSw þó

OE Cognate

þēah 'though, although, yet'

Phonological and morphological markers

ON /au/ &lt; PGmc */au/

Summary category

A1*c

Attestation

Common since ChronE s.a. 1135.  On the diffusion of this word southwards and westwards during the ME period, see Samuels 1972: 70–2.  LAEME (see esp. dot maps 01988707, 01988708, 01988709) shows forms with likely ON input predominantly from the N/EM (contrast maps 01988704, 01988705, 01988706 for native forms, which are mainly SM and S); whereas by LALME (dot maps 191–208) the Norse-derived forms are widespread (and native forms are now restricted to the SM and S).

Occurrences in the Gersum Corpus

Gaw 69, 624; Pe 345; Erk 320; WA 51, 254, 471 etc.

PS introduce a further instance of this word at Gaw 1799, by emending MS <of> (usually corrected instead to *if, as in TGD).

Bibliography

MED though (conj.) , OED though (adv., conj. and n.) , HTOED , Dance þoʒ, Bj. 72-4, 181, SPS 486, de Vries þó, Mag. þó, Orel *þat, AEW ðēah