(1) (*þwarte-knot) ‘cross knot’; (2) (þwarle knot) ‘tight knot’, ‘intricate knot’, ‘twirled knot’(Modern English (1) thwart; (2) thwarl)
The possibility of Norse derivation here requires an emendation of the MS reading (see Discussion by Text) of Gaw 194 (‘Syþen þrawen wyth a þwong a þwarte-knot alofte’): (1) GDS's suggested emendation *<þwarte>, not actually printed in the edition (see further Discussion by Text) would identify it with ME thwert (adj.) ‘crosswise, transverse’ to produce a compound meaning ‘cross-knot, i.e. an ornamentation going cross-wise’. ME thwert is always derived from ON, neut./adv. of þverr ‘athwart, across, transverse’ < PGmc *þwerxwa- (cp. OE þweorh ‘cross, transverse (etc.)’, Go þwaírhs (‘angry’), OFris (adv.) thweres, OS thwerh (‘stupid’), OHG twerh, dwerah) (see further ouerþwert above), and GDS compares in particular the OIcel compound v. þver-knýta ‘to knit with a cross knot’. This is plausible, though it should be added that the late ME change /ɛr/ > /ar/ required by *þwarte- is not well attested in the Gaw MS, and there are no instances of ME thwart spelt with <ar> recorded by MED until the 15c. (contrast Gaw ouerþwert). (2) The MS reading þwarle is retained by all other authorities since Madden, who compares Lan. dial wharl-knot 'a hard knot' (see EDD), a good analogue in terms both of sense and form, given the change /θw-/ > /hw-/ of which there are a number of instances in N MnE dial (see Onions 1924: 204, Hamp 1989, Thorson 13). An etymology for this ME thwarl- is more elusive: (a) TGD tentatively explain it as related (in an undefined way) to OE þweorh ‘cross, transverse’ (see further (1)), and gloss ‘intricate knot’. (b) Others (GDS 194n and PS 194n) have explored an identification with OED’s thwerl v., which is attested only once c. 1490 in Caxton’s Foure Sonnes of Aymon (i.32: ‘Reynawde … thwerled his swerde by grete fyersnesse’). PS suggest a relationship to to twirl (< OE thwer-), but the etymology of twirl (not attested till 1598) is difficult itself. Both could share an origin in the root of PGmc *þweran- (as in OE (ge)þweran ‘to stir, churn; beat, forge, render malleable, soften’, OHG gidweran ‘to stir up’), denoting swirling or stirring which might plausibly develop into a word describing a type of knot. However, as with (1), this would require a late ME /ɛr/ > /ar/, and we might more plausibly posit as etymon the a-grade *þwar-, as in OIcel þvara ‘whisk’, OHG twaron ‘to move in a confused way’. (c) A final alternative requires the most conjecture: twirl and thwerl have both been explained as (ideophonic) by-forms of whirl (as EDD's lemmatization of wharle knot under whirl n. suggests). In that case, the ultimate origin is in a form of PGmc *xwerƀan- ‘to turn, change’ (etc.) (see the etymological discussion of wyrles on the possibility of ON input). However, assuming we do not simply have a kind of ad hoc, ideophonic lowering (ME hwirl- > hwarl-), we would again need to consider the a-grade of the root (PGmc *hwarƀ-) as the most plausible starting point, the nearest recorded forms then being OFris hwarvel, OHG hwerbel, Du wervel, and probably also OE (late WS) hwyrfel ‘circuit, exterior, higher part’.
(1) *þwerxwaz; (2b) *þwer- or *þwar-; (2c) *xwerƀan-
Proposed ON Etymon (OIcel representative)
(1) þverr ‘athwart, across, transverse’
(ONP (1) þverr (adv.); þver-knýta (vb.))
Other Scandinavian Reflexes
(1) Far tvørur, Icel þver, Norw tver, ODan thwær, Dan tvær, OS þvær, þvar
(1) þweorh ‘cross, transverse (etc.)
Phonological and morphological markers
ON adjectival (adverbial) -t] (may not be applicable)
[ON loss of */x/ finally] (may not be applicable)
A hapax legomenon in both its emended and unemended forms. (1) The simplex ME thwert is widespread and common (though confined to the N in place-names). (2) The compound wharl-knot is recorded as a Lan. dial word in EDD.
Occurrences in the Gersum Corpus
GDS (194n) suggests emending Gaw MS <þwarle-> to *<þwarte-> at 194 (but prints <þwarle-knot>) (see further Etymological Discussion (1)), but all other authorities maintain the manuscript reading <þwarle->.
MED thwarle (adj.) , OED thwarl (adj.) , HTOED , Dance þwarte-knot; (1) MED thwert (adj.) , MED thwert (adv.) , OED thwart (adv., prep., and adj.) , de Vries þverr, Mag. þver, Bj-L. tverr, Heid. þwerha-, Orel *þwerxwaz, Kroonen *þwerha-, AEW ðweorh, EPNE þverr, Bj. 19, 224; (2) EDD whirl (v., sb.) sense (7); (2a) Heid. þwerha-, Orel *þwerxwaz, Kroonen *þwerha-, AEW ðweorh; (2b) OED thwerl (v.) , OED twirl (v.1) , Seebold þwer-a-, Kroonen *þweran-, AEW ðweran; (2c) MED whirlen (v.) , OED whirl (v.) , Seebold hwerb-a-, AEW hwierfel