< Kelt.; Ml. W. nywl § 90, di̯awl § 100 ii (1).—ml, mr § 99 ii.—mn § 76 vii, § 99 iv.
Other groups of explosive + sonant are regular.
§ 105. i. After r Brit. and Lat. p, t, k become respectively ff, th, ch; thus W. corff < Lat. corpus;—W. gorffwys § 89 ii (2);—W. porth < Lat. portus;—W. archaf § 63 iii, etc.
lk > lch, as W. golchi § 89 ii (2);—W. calch < Lat. calc-em.—lp > lff, as W. Elffin < Gallo-Lat. Alpīnus.—lt > llt, as in Ml. W. kyfeillt ‘friend’ = Ir. comalte ‘foster-brother’ < *kom-alt(i)i̯os; W. allt ‘declivity; grove’ < *alt‑, √al- ‘grow, nourish’: Lat. alo, altus; medially it becomes ll as in W. cyllell ‘knife’ < Lat. cultellus; W. di-wylli̯o ‘to cultivate’: gwyllt ‘wild’ § 92 iv; except in re-formations, as in hollti ‘to split’ from hollt § 96 iv (1); the t is sometimes lost finally in an unstressed syllable, as in Mn. W. cyfaill, Ml. and Mn. deall § 75 vi (4).
ii. rb > rf, as in W. barf ‘beard’ < Lat. barba; also rw̯, as in sýberw̯ ‘proud’ < Lat. superbus.—rd > rẟ, as in bardd < Brit. *bardos (βαρδοί· ἀοιδοὶ παρὰ Γαλάταις, Hesych.).—Medially rg > ri̯ as in ari̯an ‘silver’ = Ir. airget < Kelt. *argn̥t-om: Lat. argentum, Skr. rajatá‑m: Gk. ἄργυρος, √areg̑‑. Finally rg > ‑r, ‑rỿ, ‑ra, ‑rw̯ § 110 ii.
lb > lf, as in gylfin ‘beak’, O. W. gilbin: Ir. gulban id. < Kelt. *gulb‑.—Medially lg > li̯, as in dali̯af § 110 ii (2); for final lg see ib.—Medially ld > ll as in callawr ‘caldron’ < Lat. ´caldārium;—finally llt as in swllt ‘money, shilling’ < Lat. sol’dus.
iii. rm > rf or rw̯ § 99 ii (2);—lm > lf, ib.;—nm > nf or nw̯ § 99 iv (1).
The Nasal Mutation.
§ 106. i. (1) A nasal before an explosive was assimilated to it in position where it differed; thus Ar. k̑m̥tóm ‘100’ > Brit. *kanton; Ar. *penqu̯e ‘5’ > Kelt. *qu̯eŋqu̯e > Brit. *pempe. This may be assumed to have taken place in Late Brit. when the nasal ended one word and the explosive began the next if the syntactical connexion was a close one. Subsequently a media, or (later) a tenuis, was assimilated to the nasal, becoming itself a nasal. This is called the “nasal mutation” of the explosive.
