[1] The headword phrase appears also in other lexica (references at Photius upsilon205 Theodoridis), with the same or similar glossing of the element of it glossed here (the present active participle, neuter nominative/accusative singular, of u(poikoure/w); variants of the first glossing participle are u(postrefo/menon "turning around" and u(potrefo/menon "being fostered". The source of the headword phrase as a whole seems to be a scholion on Lucian (214.14 Rabe), where likewise it appears with this glossing -- but Lucian's own phrase (Abdicatus 6) is different: ti palaio\n u(poikourou=n e)n th=| yuxh=| kako/n. 'Lurking hatred' is an idiom also found in Nicolaus of Damascus and in Josephus.
[2] For Tullus cf. pi 344. The present quotation (transmitted, in Adler's view, via the Excerpta Constantini Porphyrogeniti) was not identified by Adler, but latterly Favuzzi [see under alpha 1596] 196-197 finds vocabulary-based arguments for attributing it to Aelian. They include the verbs u(potara/ssw and u(poikoure/w and the phrase h(suxh|= pws. Favuzzi also notes that Bernhardy's proposed emendation of u(pela/nqanon to u(polanqa/non -- thus producing a translation along the lines of 'even if there was nothing lurking and hidden' -- would create another link with Aelian.