Pylimitics

In software development the word “deprecate” has come to mean “no longer to be used.” This is actually jargon; “deprecate” isn’t used that way in any other context. It originally comes from the Latin word “deprecari,” which means to “pray against.” “Deprecate,” when it appeared in the 1600s, meant a prayer — specifically a prayer to repel evil or reverse its effects. Robert Lowth was Bishop of Winchester in the 1700s and used the word this way:

“Evil shall come upon thee, which thou shalt not know how to deprecate.”

(That’s from his translation of the book of Isaiah.)

“Deprecate” has a fairly close homonym: “depreciate,” which is similar in sound and usage but not related at all etymologically. “Depreciate,” which is slightly older word, comes from “depretiare” (undervalued). Its meaning hasn’t shifted as much as “deprecate.” “Deprecate” has shifted quite a lot in meaning. It lost the sense of “prayer” by the 1800s and came to mean “expressing earnest disapproval,” but not in any specific way. After another century the meaning shifted include belittling or disparaging. Not a big change, but enough for the grammarians of the time, who warned that “deprecate” shouldn’t be used that way because it was getting too close to “depreciate” or “lowering of value.” Although the “value” was ostensibly something close to financial, there was also a sense in which a reputation could be depreciated. 

Language usage guides kept up the warning about keeping the two words distinct for another century; the second edition of Fowler’s Modern English Usage (published in 1965) says plainly that confusing them is “a blunder.” But that attitude began to relax around that time; the third edition of the same reference just suggests users should “keep the historical distinction in mind,” and points out that “depreciate” was becoming restricted to the financial sense and “deprecate” was being used in other contexts. 

“Deprecate” probably became software-industry jargon when it began to be used in the development of specification documents. When the spec team “disapproved” of a certain detail the document history would describe the old section as “deprecated.” The word is even defined in Request for Comments (RFC) 1158 from May, 1990:

“In order to better prepare implementors for future changes … a new term ‘deprecated’ may be used when describing an object. A deprecated object … is one which must be supported, but one which will most likely be removed from the next version …”

If you continue to use the “deprecated object,” your work will doubtless depreciate apace.