Originally, to send to, as a message; hence, by letter. The kindred noun ἐπιστολή, whence our epistle, means, originally, anything sent by a messenger. Letter is a secondary meaning.
Pollutions (ἀλισγημάτων)
A word not found in classical Greek, and only here in the New Testament. The kindred verb ἀλισγεῖν, to pollute, occurs in the Septuagint, Daniel 1:8; Malachi 1:7, and both times in the sense of defiling by food. Here the word is defined by things sacrificed to idols (Act 15:29); the flesh of idol sacrifices, of which whatever was not eaten by the worshippers at the feasts in the temples, or given to the priests, was sold in the markets and eaten at home. See 1Co 10:25-28; and Exo 34:15.
Fornication
In its literal sense. “The association of fornication with three things in themselves indifferent is to be explained from the then moral corruption of heathenism, by which fornication, regarded from of old with indulgence, and even with favor, nay, practised without shame even by philosophers, and surrounded by poets with all the tinsel of lasciviousness, had become in public opinion a thing really indifferent” (Meyer). See Döllinger, “The Gentile and the Jew,” ii., 237 sq.
Strangled
The flesh of animals killed in snares, and whose blood was not poured forth, was forbidden to the Israelites.