The phrase "is first attested" is correct and usable in written English.
It is typically used in historical or linguistic contexts to indicate the earliest known occurrence of a word, phrase, or concept.
Example: "The term 'internet' is first attested in the early 1970s."
Alternatives: "is first recorded" or "was first documented".
It is first attested in the inscriptions of Darius I (ruled 522 486 bce), of which the longest, earliest, and most important is that of Bīsitūn.
Indo-European is first attested in Anatolia in names occurring in Middle Bronze Age tablets from Kültepe, but the date, route, and even the reality of an Indo-European invasion or infiltration are all controversial.
Writing, which is first attested at the middle of the 4th millennium bce, was in its origins predominantly logographic (i.e., each word or morpheme was represented by a single graph or symbol) and long remained a highly imperfect means of rendering the spoken word.
Perhaps the most famous of the Pythagorean dietary restrictions is the prohibition on eating beans, which is first attested by Aristotle and assigned to Pythagoras himself (Diogenes Laertius VIII. 34).
Its presence in Edinburgh is first attested by a long and enthusiastic account published in the Edinburgh Review in February 1816, authored by the geologist Leonard Horner, future father-in-law of Charles Lyell.
The style is first attested at Mithridatkert/Nisa.
The word was first attested in English in 1691 in the form orang-outang, and variants with -ng instead of -n as in the Malay original are found in many languages.
Although the counties in Transylvania were first attested from the 1170s, earlier references to fortresses at their seats and archaeological finds suggest that a system of counties existed in the 11th century.
Greek settlement is first clearly attested by the presence of pottery dating from about 1000 bce.
Robert's successor as dean, Robert Butevilain, is first securely attested as dean on 6 May 1158, and the last secure date for his holding his previous office is 13 December 1157, which suggests that Robert of Ghent died in between those dates, or shortly before the earlier date.
He became an Augustinian canon at Cirencester Abbey before becoming prior of the priory of St Frideswide in Oxford, an office he occupied from sometime before the end of 1139, when he is first securely attested in the office, until after 1174, his last appearance as prior.
