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Published 01/10/24
cràigheadh m. [ˈkɾaːˌjaɣ], 
Cf. McDonald 1972: cràighiadh.
gen. cràigheoidh [ˈkɾaːˌjɔj], or crà-ghèadh [ˈkɾaːˌjiaɣ], 
Cf. Faclan bhon t-Sluagh˄: [kɾɑ:jıɑɣ], North Uist, and (the normalised oblique form) [kɾɑ:ȷɑi], Harris.
gen. crà-gheòidh [ˈkɾaːˌjɔːj], ‘shelduck, Tadorna tadorna’ is tentatively derived by Goodrich-Freer (1897, 68: cràghiadh) from ON kráka f. ‘crow’, although ON kráka would formally yield SG *[ˈkʰɾaːɡ̊ə]. McDonald (2009, 377; 2015, 126–27) considers the loan unlikely, noting the form cràdh-ghèadh (Dwelly 1911), ‘which loosely translates as “anguish/torment + goose”, possibly a reference to protective behaviours of the species.’
The second element of this bird name is SG gèadh (sometimes written giadh) m. ‘goose’ (EG géḋ). Confusion of the first element with cràdh m. ‘pain, anguish’ and cnàimh m. ‘bone’ is long-standing: Shaw (1780) lists on the one hand cradhgheadh, with a cross-reference to cnamhgheadh, and on the other (pl.) cnaimhgheoidh ‘a bird between a goose and a duck’, 
Borrowing from Shaw, O’Reilly’s (1817) Irish dictionary lists cradhgheadh, with a cross-reference to cnaimgheoidh (sic), but omits the entry for cnaimhgheoidh.
so Armstrong (1825: cnaimh-gheadh 
Cf. SG cnàimh-fhitheach m. ‘raven’, cnàimheach ‘a member of the crow or corvid family of birds’.
) and HSS (1828: cràdh-ghèadh).
The shelduck is larger than a mallard but smaller than a goose. It has a dark green head, a red beak and pink legs and feet; additionally, it has a russet breast band over a white body, hence its English name shelduck (< sheld- ‘pied’). Noting the colour of its beak and breast band, Garvie (1999, 59) explains the first element of the Gaelic name means ‘red’, cf. SG cràidhearg 
Cf. Dieckhoff 1932: craidhearg [kraːijèrag].
, crà-dhearg, crò-dhearg adj. ‘crimson, lit. blood-red’, a closed compound consisting of SG †crò ‘blood’ (EG cró, crú 
Greene 1983, 6–7.
) + dearg ‘red’ (EG derg), cf. Ir. cródhearg ‘blood-red’ (Ó Dónaill 1977); cf. also SND˄ (s.v. craw IV B), which notes the Gaelic word was borrowed into Scots as craajuck, crawjuck and translates crà-gheadh (sic) as ‘red-goose’. Compare the use of cràidhearg to refer to the russet colour of deer, e.g. fiadh crà-dhearg (Loch Aillse 1873, 260) and heather, e.g. fraoch cro-dhearg (Mac Gille Sheathanaich 1917, 172), where there has conceivably been conflation between crà and †cròn ‘brown, swarthy’ (Dwelly 1911; Shaw 1780: cron ‘brown, dun-coloured, red, swarthy’) (EG crón ‘brown, reddish-brown, dark yellow, red (?)’ (eDIL˄)).
≈CG II, 250–01, lists several examples of crà ‘blood, hence red’ in compounds, including crà-dhearg ‘blood-red’, crà-dhubh ‘dark red’, crà-gheal ‘light red’, crà-chù ‘fox’, crà-ghèadh ‘shelduck’ and, anomalously, crà-fhaoileag ‘red gull’, identified as ‘the black-headed gull generally called ceann-dubh and ceann-dubhan “black-headed”’, although here there may be conflation with cnàimh-. Forbes (1905, 25, 332) includes cra-gheal (sic) for ‘shelduck’, but this is probably in error.