From pros and tithemi; to place additionally, i.e. Lay beside, annex, repeat -- add, again, give more, increase, lay unto, proceed further, speak to any more.
see GREEK pros
see GREEK tithemi
1. properly, to put to.
2. to add, i. e. join to, gather with any company, the number of one's followers or companions: τινα τῇ ἐκκλησία, Acts 2:47 (R G); τῷ κυρίῳ, Acts 5:14; Acts 11:24; namely, τῷ κυρίῳ, or τοῖς πιστεύουσιν, Acts 2:41; Hebraistically, προσετέθη πρός τούς πατέρας αὐτοῦ (Judges 2:10; 1 Macc. 2:69), he was gathered to his fathers assembled in Sheol (which is לְכָל־חָי מועֵד בֵּית, the house of assembly for all the living, Job 30:23), Acts 13:36 (others explain it, he was added to the bodies cf his ancestors, buried with them in a common tomb; but cf. Knobel on Genesis 25:8; (Böttcher, De inferis, p. 54ff)); equivalent to to add viz. to what one already possesses: τί, Luke 17:5 (A. V. here increase); passive, Matthew 6:33; Luke 12:31; Mark 4:24; Hebrews 12:19 ((μή προστεθῆναι αὐτοῖς λόγον, R. V. that no word more should be spoken to them)); — to what already exists: (ὁ νόμος) προσετέθη, was added to (supervened upon) namely, the ἐπαγγελία, Galatians 3:19 R L T Tr WH; τί ἐπί τίνι, some thing to (upon) a thing (which has preceded (cf. ἐπί, B. 2 d.)), Luke 3:20; τί ἐπί τί, to a thing that it may thereby be increased, Matthew 6:27; Luke 12:25. In imitation of the Hebrew (יָסַף) the middle (in the Sept. the active also) followed by an infinitive signifies (to add, i. e.) to go on to do a thing, for to do further, do again (as Genesis 4:2; Genesis 8:12; Genesis 18:29): προσέθετο πέμψαι (לִשְׁלֹחַ וַיֹסֶף), he continued to send (as be had already sent), Luke 20:11, 12 (equivalent to πάλιν ἀπέστειλεν, Mark 12:4); προσέθετο συλλαβεῖν καί Πέτρον, be besides apprehended Peter also (A. V. he proceeded etc.), Acts 12:3; in the same way also the participle is used with a finite verb: προσθείς εἶπεν, i. e. he further spake (A. V. he added and spake), Luke 19:11 (προσθεῖσα ἔτεκεν, Genesis 38:5; προσθέμενος ἔλαβε γυναῖκα, Genesis 25:1); cf. Winers Grammar, § 54, 5; Buttmann, § 144, 14.