thira

adjective solid, hard, firm; strenuous, powerful Ja.i.220 Ja.iv.106 (= daḷha); Mil.194 (thir-âthira-bhāva strength or weakness); Vv-a.212 (id.), Vv-a.35 (= thāmavant); Sdhp.321.

Vedic sthira, hard, solid; from sthā or Idg. ster (der. of stā) to stand out = to be stiff; cp. Gr.στερεός; Lat. sterilis (sterile = hardened, cp. Sk. starī) Ohg. storrēn, Nhg. starr & starren, E. stare; also Lat strenuus