From keimai; a couch; by extension, cohabitation; by implication, the male sperm -- bed, chambering, X conceive.
see GREEK keimai
a. a place for lying down, resting, sleeping in; a bed, couch: εἰς τήν κοίτην (see εἰμί, V. 2 a.) εἰσιν, Luke 11:7.
b. specifically, the marriage-bed, as in the Tragg.: τήν κοίτην μιαίνειν, of adultery (Josephus, Antiquities 2, 4, 5; Plutarch, de fluv. 8, 3), Hebrews 13:4.
c. cohabitation, whether lawful or unlawful (Leviticus 15:4f, 21-25, etc.; Wis. 3:13, 16; Euripides, Med. 152; Alc. 249): plural sexual intercourse (see περιπατέω, b. α.), Romans 13:13 (A. V. chambering); by metonymy, of the cause for the effect we have the peculiar expression κοίτην ἔχειν ἐκ τίνος, to have conceived by a man, Romans 9:10; κοίτη σπέρματος, Leviticus 15:16; Leviticus 22:4; Leviticus 18:20, 23 (here κοίτη εἰς σπερματισμόν); on these phrases cf. Fritzsche, Commentary on Romans 2, p. 291f.