assumption

First recorded in 1250–1300; Middle English assumpcioun, assompcioun, assumsion, from Latin assūmptiōn- (stem of assūmptiō ), equivalent to assūmpt(us) “taken up” (past participle of assūmere ) + -iōn- noun suffix; see origin at assume, -ion

The word assumption is a great example of how a word can take on new dimensions of meaning over time, while staying true to some aspect of its original sense.
assumption has been in the language since the 13th century, and was initially confined to a specific ecclesiastical meaning in the Catholic Church. The Latin word on which it is based literally means “the action of being taken up or received,” and in English assumption referred to the taking up into heaven of the Virgin Mary. That meaning still exists today, and in all the meanings it has assumed since then, one can see the common thread running through them is the sense of taking.
One early sense meant “arrogance,” as in this 1814 quote from Sir Walter Scott: “his usual air of haughty assumption.” Arrogance is a taking upon oneself a conviction of self-importance. Later senses arose having to do with the taking on of power or other responsibilities, as in “the assumption of command.”
Probably the most common meaning of assumption in use today is for indicating a supposition, an estimate, a conjecture—that is, something taken for granted. And as any schoolkid knows, presuming to assume can be dangerous, leading us to make, as the saying goes, “an ASS of U and ME!”

—Assumption persona: A persona is a detailed description of a fictional user (of a product, software program, etc.), based on real-world data. Software engineers and data companies create personas as user models to help build their products. In order to illustrate the utility of using data-driven personas in design, “assumption personas” (personas derived from existing assumptions about users) are used as negative examples showing how assumptions can lead to bad design choices.
—Assumption of risk: the name for a defense used in tort law, where the defense argues that the plaintiff took action knowing the risks involved.