Whence "בחזקת בשרי"?

Question

Besides the main categories of meat, dairy, and pareve (non-meat, non-dairy) foods, two special subcategories of pareve foods are relevant to halacha (e.g. Yore Dea 93): pareve food cooked using clean meat utensils, and pareve food cooked using clean dairy utensils.

In America, those foods are colloquially known as "[meat/dairy/other words] kelim" or "[meat/dairy/other words] equipment". (Kelim means "receptacles".) In fact, what's probably the largest kashruth supervisory agency in the United States, the Orthodox Union, has in the past allowed products to have a "DE" certification mark, signifying "dairy equipment". And this all makes a lot of sense: the phrase "dairy equipment", or "meat kelim", or the like, refers, as a metonym, to the food that was prepared on such equipment.

In Israel, on the other hand, those foods are called "b'chezkas [b'sari/chalavi]", "with/in a chazaka of [meat/dairy]". In its normal uses in halacha, "chazaka" is probably best translated "status": it refers to the state that something or someone is in or can be presumed to be in absent evidence of a change of state. So these foods are called "with a status of meat" or "with a presumption of dairy" or the like. Why? They're not meat or dairy themselves; nor is there any halachic chazaka (that I know of) that says that they are. Where does this "b'chezkas" wording come from and why is this state referred to by this terminology?

Answer 1

They are referred to as B'echezkat because they are always held and used for the purpose of cooking or storing said products. It also can refer to food that's pareve but was cooked in (generally) clean receptacles, so that although the food isn't strictly speaking meaty or milky, it may not be eaten together.

Answer 2

In Israel you will often find foods considered בחזקת בשרי have parve ingredients but may have been contaminated by nearby meat foods, such as french fries in a fast-food schwarma restaraunt.

According to sefardic halachic tradition, "meat equipment" is an irrelevant category. It is identical to parve. But "chezkat besari" cannot be considered parve.