It was a modest circumlocution used to avoid the use of " I " which might have seemed arrogant.
9 The phrase Mal'akh Yahweh may have been originally a courtly circumlocution for the Divine King; but it readily became a means of avoiding crude anthropomorphism, and later on, when the angels were classified, the Mal'akh Yahweh came to mean an angel of distinguished rank.
(6) No marginal notes at all to be affixed, but only for the explanation of the Hebrew or Greek words which cannot, without some circumlocution, so briefly and fitly be expressed in the text.