aetatis

(aetat or aet) aged... or 'of the age...' (precedes the age of someone/something)
Found on https://www.businessballs.com/glossaries-and-terminology/latin-terms-and-ph

aetatis

aetatis; ae., aet.; aetatis suae Aged; of age; in the year of his (or her) age. These terms are shortened versions of the more proper anno aetatis suae, 'In the year of his/her age.'. Frequently found abbreviated on old tombstones, it appears variously as A.A.S., A.S., and most commonly aet; for example, if someone died in his 41st year, the marke...
Found on http://www.wordinfo.info/words/index/info/view_unit/3055/12
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