What, my son? - The Chaldee בר bar is used twice in this verse, instead of the Hebrew בן ben, son. This verse is very elliptical; and commentators, according to their different tastes, have inserted words, indeed some of them a whole sentence, to make up the sense. Perhaps Coverdale has hit the sense as nearly as any other: "These are the wordes of Kynge Lemuel; and the lesson that his mother taughte him. My sonne, thou son of my body, O my deare beloved sonne!"
The son of my vows? - A child born after vows made for offsprings is called the child of a person's vows.
The repetitions are emphatic; expressive of anxious love.
Son of my vows - Like Samuel, and Samson, the child often asked for in prayer, the prayer ratified by a vow of dedication. The name Lemuel (literally “for God,” consecrated to Him) may be the expression of that dedication; and the warning against indulging in wine Proverbs 31:4 shows that it had something of the Nazarite or Rechabite idea in it.