The English term for a word formed from the initials of a phrase is “acronym.”
Acronyms shorten multi-word names or expressions by using their initial letters or parts. Some are pronounced as ordinary words, such as NASA, NATO, radar, and scuba. The word “acronym” itself entered English in the 20th century, influenced by German terminology.
A common mix-up is “initialism.” In a strict traditional distinction, an acronym is pronounced as a word, while an initialism is spoken letter by letter, as with FBI, BBC, or DNA. In everyday English, however, “acronym” is often used broadly for both types of abbreviation.
Acronyms can become ordinary vocabulary: “laser” began as an abbreviation for “light amplification by stimulated emission of radiation,” while “radar” came from “radio detection and ranging.” A portmanteau is different because it blends parts or sounds of words rather than simply taking initials.