-dem

Meaning

1. morphemenot comparabledemonstrative ending
   ibī (“in that place”) > ibidem (“in that very place”)
   ita (“in this way”) > itidem (“likewise”)

Origins

Latin -em Latin -dem Misinterpretation of -em. When the old ablative cases of is, eōd, eād, became eō, eā, the true forms eōd-em, eād-em were interpreted as eō-dem, eā-dem. The neuter nominative singular id-em is natural and gives earlier emem (= later eundem). The new marker -dem then served to create totidem, tantumdem, ibīdem, etc. Compare tam-en with its later doublet: tan-dem (← *tam-dem).