Tachmonite is a designation associated with Jashobeam, one of David’s chief warriors. The term is connected with Hachmonite, the family or local designation found in the parallel genealogical account.
The designation occurs in the list of David’s mighty men, where it is associated with Jashobeam and his position among the chief warriors.
The wording is connected with a textual difference between the account in Samuel and the parallel account in Chronicles. The supplied material identifies “Hachmonite” as the clearer form.