Proverbs 30:15

15. The horseleech עלוקה , ( ‘ halukah.) This word occurs nowhere else in the Bible, and the critics are by no means agreed as to its meaning. Dr. A. Clarke thinks it may have been the proper name of some well-known woman of the time. Stuart thinks it means the fabled vampire, and so translates. All the ancient versions however, render it leech, or bloodsucker. But the ancients and some moderns, according to their principles of mystical interpretation, had various notions of what it symbolized. Some of the Rabbies thought it meant “destiny,” and the two daughters, paradise and sheol. The former never has enough of the righteous, the latter of the wicked. Bochart makes the two daughters, “the grave and hell.” Calmet says, ‘halukah is covetousness, and the two daughters, avarice and ambition. All this is fanciful. Alukah, the leech, is the emblem of insatiableness, and the two daughters are probably its two suckers, whose continual cry is, “Give, give.” (See Webster’s Dictionary for a description of the leech and its two suckers.) The horseleech is a less powerful leech, commonly attacking the membranes of the month and nostrils of animals that drink at the pools where it exists. It is probable, although no comparison is expressed between the leech and the following things named, that similitude is implied. So the Septuagint understood it, or made it: The bloodsucker has three daughters well beloved, and these three were not able to fill her, and the fourth was not content to say, Enough.

Three… four It was common among the Hebrews to specify a number, and then to add another, somewhat as we say three or four. See on Proverbs 6:16.