פֶּטֶר‎ (peṭer|peh'-ter|noun|masculine|fissure|that which separates)
[Heb] פֶּטֶר‎, פִּטְרָה‎ ETCBC: פֶּטֶר‎ (subs|first-born), פִּטְרָה‎ (subs|first-born) OSHL: q.bg.ab, q.bg.ac TWOT: 1764a 1764b GK: H7081, H7082 Greek: διανοίγω, πρωτότοκος
Derivation: or פִּטְרָה‎; from פָּטַר‎;
Strong's: a fissure, i.e. (concretely) firstling (as opening the matrix)
KJV: firstling, openeth, such as open.