Both καπηλεύω and δολόω are used to express wrong treatment of the word of God. Each occurs but once, in the Second Epistle to the Corinthians. Doubtless the Apostle Paul as led of the Holy Spirit had some reason for employing different words, though others deem the two words to signify the same; as in both places in the Vulgate they are translated adulterantes. They both convey the thought of 'falsifying.'
δολόω (from δόλος, 'guile, cunning') occurs in 2 Corinthians 4:2 , where "falsifying the word" gives the true meaning. καπηλεύω conveys more than this. The noun κάπηλος signifies one who sells wine, as may be seen in the LXX in Isaiah 1:22 , "wine merchants," but it is immediately added, they "mix the wine with water." This became so common a practice that the word καπηλεύω came to imply 'making a gain by adulterating.' The word occurs in 2 Corinthians 2:17 , which may therefore be translated "traffic in," or "make gain by corrupting the word of God." The passage consequently implies that those referred to falsified the word of God with a view to some advantage to themselves. It is possible therefore that Paul in each passage refers to a different class of persons.