This etymology is found only here. It is not certain we are dealing here with a true etymology, since mekhri biou could be a mere mistake for mekhri baiou "down to the detail": the latter is one of the two competing etymologies, attested in several sources and going back to Orion at least (see ἀκριβής / ἄχρι + βαιός), but baios is a rare adjective which was no longer familiar to byzantine copyists and could easily be misread bios. However, even if this is originally a mistake, the copyist of the Gudianum took it as an etymology in its own right, and introduced it into his list as a third possibility. It has the same structure as the etymology ἄχρι + βαιός from which it is derived (mekhri being used in the text as a synonym for akhri, which is considered as the first part of the etymon), and the second element is also represented only by its initial consonant. From the semantic point of view, however, it is less satisfying, since what matches "exact" in the definition given is ζητῶν "searching", not μέχρι βίου which is only an adverbial phrase: one can do many things throughout one's life without it having anything to do with exactness. Yet the etymological relationship is established between the lemma and the adverbial phrase of the gloss, over the verb "to search" (see a similar structure in χείρων / χείρ, θύρα / θύω).