The headword derives from siro/s, a pit, vessel, or silo for storing grain (cf. LSJ s.v.), and masth/r, a searcher (cf. LSJ s.v.); (cf. Chantraine, s.v. siro/s). Tax collectors used the tool to gauge grain-fill depth in storage pits. In warfare too, this kind of rod was used to probe the ground for pit traps; see generally LSJ s.v. siroma/sths.
[1] Likewise in Photius' Lexicon (sigma237 Theodoridis), and cf. Hesychius sigma728. An alternative spelling, differing by a diphthong in the first syllable, seiroma/sths, is given with a marginal addendum to the passage in Suda ms. M (= Marcianus 448); cf. sigma 286 and Joannes Tzetzes, Chiliades 13.516-22.
[2] Eunapius fr. 49 FHG (4.36); Blockley, Eunapius fr. 46.3. This passage, together with rho 294, apparently refers to corruption during the reign of Emperor Theodosius I (The Great) (346-395; OCD(4) s.v. Theodosius(2) and theta 144) as described by Zosimus 4.28.3-4.29.2 (Blockley, p. 142).