Reversible etymology, since the opposite derivation is attested (see γῆρας / γέρας). The etymology relies on the usual alternation between [ē] and [ĕ] (τίθημι / τίθεμεν), which is a minimal change, the suffix and inflectional type of both words being identical. The semantic connection relies on the notion that old age is worthy of honor, and indeed Orion glosses γῆρας by τίμιον, which explicates the semantic relationship. The connection is correct by modern standards, although neither word is directly derived from the other.