I traced down the particular edit which added the phrasing, but couldn't find an explanation. This is a Wikipedia edit, not an authoritative source, so I wouldn't put too much thought into it.
... so let's put too much thought into it. It turns out it leads to some interesting background on the Three-Fifths Compromise.
It could be a reference to a similar debate over the status of slaves proposed as Article XI to the Articles of Confederation. Only this time the issue was determining wealth for the purposes of taxation. There was an idea put forward that states should contribute to a common national treasury according to their ability to pay, and that this ability to pay would be determined by their population.
...all charges of war and all other expenses that shall be incurred for the common defense, or general welfare, and allowed by the United States assembled, shall be defrayed out of a common treasury, which shall be supplied by the several colonies in proportion to the number of inhabitants of every age, sex, and quality, except Indians not paying taxes...
Samuel Chase of Maryland (a slave state) made the point that since this is a surrogate for determining the ability of a state to pay taxes, only the white inhabitants should be counted since they controlled most of the wealth. Slaves were considered property and "cannot be distinguished from the lands or personalities held in those states where there are a few slaves." He's saying that if you count both white and slaves as a surrogate for determining tax burden, they'll be overtaxed.
Not surprisingly, free states did not like this plan. John Adams, representing Massachusetts, countered that since this article is for the purpose of determining wealth, not representation, then a southern slave laboring in the south contributed as much as the laboring poor of the north. James Wilson of Pennsylvania put it bluntly.
...if this amendment should take place, the Southern colonies would have all the benefit of slaves, whilst the Northern ones would bear the burden. That slaves increase the profits of a state, which the Southern States mean to take to themselves; that they also increase the burden of defense, which would of course fall so much the heavier on the Northern; that slaves occupy the places of freemen and eat their food. Dismiss your slaves, and freemen will take their places.
John Witherspoon of New Jersey had this to say...
...the value of lands and houses was the best estimate of the wealth of a nation, and that it was practicable to obtain such a valuation... It has been objected that negroes eat the food of freemen, and therefore should be taxed; horses also eat the food of freemen, therefore they should be taxed.
There's your "slaves or other property".
The amendment was defeated in a partisan vote, 7 northern for, 5 southern against, with Georgia abstaining. It's particularly interesting to note that the sides would be reversed when the question was raised in the Constitutional Convention, but this time about representation.
Source: "The Growth and Origin of the American Constitution: An Historical Treatise" by Hannis Taylor, 1909, page 131.