Etymology

cp. OIcel heðan ‘hence; henceforth’. The standard form of the adv. in the Scandinavian languages with medial -ð- contrasts with the WGmc type with medial -n-, viz. OE heonan, OS, OHG hinan(a); cp. further the other adverbs expressing ‘direction away from’ in N and WGmc, viz. e.g. OIcel hvaðan, OE hwanon ‘whence’, OIcel þaðan, OE ðanon ‘thence’. A shared PGmc etymon *xin- has been suggested for both types, and therefore that the Norse forms have evolved via dissimilation (earlier *hiðan- < *hinan-) (see notably Kluge XXXX: 234, followed by e.g. de Vries, Torp NnEO and Falk-Torp). Alternatively, PGmc *xið- has been postulated as the origin of the Norse type (cp. the suffix -þ in Go hwaþ ‘whither’ and þad-ei ‘in which, where’). 

PGmc Ancestor

*xin- or *xið- 

Proposed ON Etymon (OIcel representative)

heðan ‘hence; henceforth’
(ONP heðan (adv.))

Other Scandinavian Reflexes

Far heðan(i), hiðan, Icel héðan, Norw hedan, Dan heden, Sw hädan

OE Cognate

?heonan 'hence, away'

Phonological and morphological markers

[dissimilation of ON */nan/ > /ðan/] (may not be applicable)

Summary category

B1c

Attestation

Predominantly N and E (and used by Chaucer as a northernism in CT.Rv.), inc. in the SE in early ME. 

Occurrences in the Gersum Corpus

Gaw 1794, 1879; Pe 271; WA 4487, 4565, 4650, etc.

Bibliography

MED hēthen (adv.) , OED hethen (adv.) , HTOED , Dance heþen, Bj. 163, 176, de Vries heðan, Mag. héðan, Torp NnEO hedan, Falk-Torp heden, Nielsen heden (II), Hellquist hädan, AEW hiona(n), -ane