This headword, literally 'tomb-old-man', seems to be colloquial and to have a negative connotation; cf. tau 1160 (plural). Its first attributable appearance is in a contextless two-word phrase from Aristophanes: Demiańczuk fr. 55. (Comica adespota fr. 1172 Kock, the single word tumboge/rwn, may or may not be different.) The two-word phrase also appears in Euripides (Medea 1209 and Heraclidae 167). Of course, Procopius' Secret History, from which the example here is derived, is a highly critical account. The modern American English "fossil," often applied as a term of reproach, provides an appropriate translation.
[1] cf. pi 958.
[2] A very loose adaptation of parts of Procopius, Secret Histories 6.11. On the emperor Justin see generally iota 449.
[3] cf. Hesychius tau1632.