(3) An explosive following the group remains, and the s disappears; thus W. torth ‘loaf’, Ir. tort < *torst- ‘baked’: Lat. tostus < *tors(i)tos: torreo < *torseiō; W. tarth ‘vapour, mist’ (tarth mwg Act. ii 19 ‘vapour of smoke’, tan twym tarth b.t. 38 ‘hot scorching fire’) < *tₑr’s‑t‑: Gk. τερσαίνω, √teres- ‘dry up’;—W. garth ‘promontory, hill’, Ir. gart < *g̑hₑr’st‑: Gk. χέρσος, √g̑heres- § 93 ii (3) (not to be confused with garth ‘enclosure’: Lat. hortus § 99 vi (1), § 76 vi (2)).
§ 96. i. Ar. s + tenuis remained in Pr. Kelt. In Brit. the group either remained or became a double spirant; thus sk gave either (1) sk or (2) χχ; and st gave either (1) st or (2) a sound between þþ and ss, which became ss. It is probable that form (1) occurred after a consonant, and form (2) after a vowel, being caused by a loose pronunciation of the s. Both forms occur initially and medially, and in the latter case form (1) can be shown in a large number of cases to have followed a consonant now vanished. In Ir. st gave ss, initially s‑, and the other groups remained unchanged.
Tenuis + s also became a double spirant in Brit. A media before s had become a tenuis in Ar., and gives the same result. An aspirated media before s changed it to z in Ar., thus dhs > dhz (dzh); the group became tenuis + s in Kelt., with the same result.
When s is combined with two explosives in any order it is the first explosive that drops: thus llost < *lompst- ii (3); asgwrn < *ast-korn- ii (4); nos < *nots< *noqu̯ts ii (5). The same simplification took place later in words borrowed from Lat.: W. estron ‘stranger’ < extrāneus, astrus < abstrūsus, etc., § 103 i (5).
ii. (1) Ar. st- became s- in Ir., st- or s- in Bret., Corn., and W. Examples: Ir. sāl, W. sawdl, Bret. seul ‘heel’ < *stā‑tl- 63 vi (1); Bret. steren, Corn. steren, W. seren ‘star’: Lat. stella < *ster-lā, Gk. ἀστήρ, O. H. G. sterno, E. star: Ar. *stē̆r‑;—Bret. staon ‘palate’, W. safn ‘mouth’: Gk. στόμα;—Ir. sere, W. serch ‘love’, Bret. serc’h ‘concubine’: Gk. στέργω: Ar. *sterk/g‑;—W. (y)starn, Bret. starn, stern ‘harness’ beside W. sarn ‘causeway’ 63 vii (2), √sterō- ‘spread out’. It is not to be supposed that st- became s- in W. in seren etc. after the separation of W. and Corn., since Lat. st- generally remains (not always; swmbwl
