Does the Catholic word Priest actually mean "Presbyter?" Or is it a conflation of roles? The problem as I understand it is a combining of roles.. not confounding or mixing  but fusing the roles into something different. The role of the priest doesn't seem to match the role of the Presbyter. But if they are the same, then why the difference.
Priest (sacerdos)

Sacerdos literally means "a giver of the sacred". St. Jerome, in his Vulgate Latin translation, uses sacerdos to translate ἱερεύς, for example in Hebrews 7:17:


  μαρτυρεί γαρ ότι συ ιερεύς εις τον αιώνα κατά την τάξιν Μελχισεδέκ
  
  Contestatur enim : Quoniam tu es sacerdos in æternum, secundum ordinem Melchisedech.
  
  For he testifieth: Thou art a priest for ever according to the order of Melchisedech.


Presbyter (senior)

The OED says this regarding "presbyter":


  The Vulgate regularly renders Greek πρεσβύτερος ["old man"], πρεσβύτεροι  by Latin senior [from senex], (plural) seniores ["ancients"], except in Acts 20:17, 22:5, where it has majores natu ["ancients"], and in Acts 14:22, 15:2, 1 Timothy 5:17, 19, Titus 1:5, James 5:14, where the Greek form is retained as presbyter, presbyteri ["priests"]. The same men who in Acts 15:2 are called apostoli et presbyteri ["apostles and priests"], are called in verses 4, 6, 22, 23 apostoli et seniores ["apostles and ancients"]; the Greek having uniformly ἀπόστολοι και πρεσβύτεροι.