Correspondence
Frey was intensely mourned by Swiss and English friends as a brilliantly gifted and lovable man. James Ussher wrote that his death "pained his heart" and as late as 1653 fondly remembered the intellectual exchanges he enjoyed when "our Frey was among the living". His correspondence, which was transcribed as part of the SwissBritNet project , shows that his linguistic skills included - beyond the usual theologian’s tools of Latin, Greek, Hebrew, Syriac and possibly Arabic – fluent and idiomatic French, Italian and English. Ordained in Westminster at age 23, he must have spoken English well enough to preach even then, and he corresponded in English with scholars such as Ussher and John Gregory (who usually carried on international exchanges in Latin) as well as with aristocratic lords and ladies such as Frances Clifford and her daughter Elizabeth Boyle. Among the tens of thousands of seventeenth-century letters in the University Library of Basel, there are just over 100 items in English, most of which were written by or to Frey.
In fact, letters written to Frey make up the bulk of the papers that we still have. He archived his correspondence carefully, made precise notes on when he had received and answered letters and kept drafts and copies of some of his own. Sadly, his correspondents were less careful, and the vagaries of the English Civil War did not help: dozens of Frey's letters are only known to us as mentions. Maybe further research will turn up some more of his lost writings, which also include a Greek poem (hodoeporicon) on his travel experience published in Geneva and the text of his inaugural lecture on the Greek language.
Regula Hohl Trillini, "Johann Jacob Frey (1606-1636)", République des Lettres 2024, https://republique-des-lettres.ch/actor/freyen.