Lexical Definition

‎ἀνήκω‎ anḗkō (an-ay'-ko) be fitting ^G:V
from ‎ἀνά‎ and ‎ἥκω‎

convenient, be fit.

• to attain to, i.e. (figuratively) be proper

Abbott-Smith

ἀν-ήκω (ἀνά, ἥκω), [in LXX: Jos 23:14 (בּוֹא), I Ki 27:8, Si. prol. 10, I, II Mac6*;]
prop., to have come up to; in later writers, impers. it is due, it is befitting: in ethical sense (MM, VGT, s.v.), Eph 5:4, Col 3:18; τὸ ἀνῆκον, Phm 8.†

Abbott-Smith References

Liddell-Scott-Jones

ἀνήκω,

to have come up to a point, reach up to, of persons and things, ἐς μέτρον τινὸς ἀ.[Refs 5th c.BC+]; φρενῶν ἐς τὰ ἐμεωυτοῦ πρῶτα οὔκω ἀ. have not yet reached the highest point I aim at, [Refs]; ἀ. εἰς τὸ ὀξύ to rise to a point, [Refs 2nd c.AD+]; τοῦτο μὲν ἐς οὐδὲν ἀ. amounts to nothing, [Refs 5th c.BC+]; μεῖζον ἀ. ἢ κατ᾽ ἐμὰν ῥώμαν the matter has gone too far.., [Refs 5th c.BC+]have gone as far as.., [Refs 5th c.BC+]

__2 ἀ. ἐς σὲ ἔχειν it has come to you to have, has become yours to have, [Refs 5th c.BC+]
__3 ἀ. εἴς τι refer to or be connected with.., [Refs 4th c.BC+]; τὰ εἰς ἀργυρίου λόγον ἀ. ἀδικήματα which involve a money consideration, [Refs 5th c.BC+]
__II belong, appertain, [LXX+3rd c.BC+]; τὰ ἀ. τοῖς ἱεροῖς[Refs 2nd c.BC+]
__II.2 absolutely, to be fit or proper, [NT]; τὸ ἀνῆκον, ={τὸ προσῆκον}, [NT]
__III come back, εἰς τοὺς πρώτους πάλιν ἀ. λόγους[Refs 5th c.BC+]

_{LSJ Scripture Refs: Eph.5.4 ☩ Col.3.18}