1520s, "act of entering," from French entrance, from entrer (see enter). Sense of "door, gate" first recorded in English 1530s. Meaning "a coming of an actor upon the stage" is from c. 1600.
curtain hung at the doorway or entrance to a room," 1843, from French portière, which is formed in French from porte "door," or from Medieval Latin portaria, fem. singular of Latin portarius "belonging to a door or gate," from porta "city gate, gate; door, entrance," from PIE root *per- (2) "to lead, pass over."
A curtain hung at a doorway, or entrance to a room, either with the door or to replace it, to intercept the view or currents of air, etc., when the door is opened, or for mere decoration. [Century Dictionary]
1610s, "allowable," from French admissible, from past participle stem of Latin admittere "allow to enter, admit, give entrance," from ad "to" (see ad-) + mittere "let go, send" (see mission). Meaning "capable of being allowed entrance" is from 1775; specific sense of "capable of being used in a legal decision or judicial investigation" is recorded from 1849.