From pleroo; repletion or completion, i.e. (subjectively) what fills (as contents, supplement, copiousness, multitude), or (objectively) what is filled (as container, performance, period) -- which is put in to fill up, piece that filled up, fulfilling, full, fulness.
see GREEK pleroo
1. etymologically it has a passive sense, that which is (or has been) filled; very rarely so in classical Greek: a ship, inasmuch as it is filled (i. e. manned) with sailors, rowers, and soldiers; ἀπό δύο πληρωματων Ἐμάχοντο, Lucian, ver. hist. 2, 37; πέντε εἶχον πληρώματα, ibid. 38. In the N. T. the body of believers, as that which is filled with the presence, power, agency, riches of God and of Christ: τοῦ Χριστοῦ, Ephesians 4:13 (see ἡλικία, 1 c. (cf. Winers Grammar, § 30, 3 N. T; Buttmann, 155 (136))); 2. that which fills or with which a thing is filled: so very frequently in classical Greek from Herodotus down; especially of those things with which ships are filled, freight and merchandise, sailors, oarsmen, soldiers (cf. our 'complement' (yet cf. Lightfoot as below, p. 258f)) (of the animals filling Noah's ark, Philo de vit. Moys. ii. § 12); πλήρωμα πόλεως, the inhabitants or population filling a city, Plato, de rep. 2, p. 371 e.; Aristotle, polit. 3, 13, p. 1284{a}, 5; 4,4, p. 1291a, 17; others. So in the N. T. ἡ γῆ καί τό πλήρωμα αὐτῆς, whatever fills the earth or is contained in it, 1 Corinthians 10:26, 28 Rec. (Psalm 23:1 3. fullness, abundance: John 1:16; Colossians 1:19; Colossians 2:9; full number, Romans 11:25. 4. equivalent to πλήρωσις (see καύχημα, 2), i. e. a fulfilling, keeping: τοῦ νόμου (see πληρόω, 2 c. α.), Romans 13:10. For a full discussion of this word see Fritzsche, Ep. ad Romans, ii., p. 469ff; (especially Lightfoot's Commentary on Colossians, p. 257ff).