peh

This is the everyday meaning of the word and the root of every other one. It names the physical mouth of a person or animal, the part of the face that takes in food and gives out sound.

Because the mouth is where words come from, Hebrew lets the same word stand for the speaking itself. What a person says can simply be called their mouth, and to put words in someone's mouth is to tell them what to say. The most weighted form of this is the mouth of the LORD, which does not picture a body part at all but means God's own spoken word, command, or promise. A prophet can even be called someone's mouth: Aaron speaks for Moses the way a mouth speaks for the person behind it.

Most occurrences of the word fall on the speaking side rather than the anatomical one, because the Bible cares far more about what people and God say than about the organ itself. The senses below run along that single line, from the physical mouth to the words it produces.

Hebrew speaks of the opening of an object the way it speaks of a mouth, because an opening is where something goes in or comes out. A well, a sack, a cave, and the pit of death all have a mouth, and when the ground swallows people the earth is said to open its mouth.

The edge of a sword belongs here through the same picture. A sword is imagined as devouring those it strikes, so its cutting edge is its mouth. The common phrase that English renders as "putting a city to the sword" is, word for word, striking it at the mouth of the sword.

A related idiom stretches the word to mean sheer extent: to fill a place from mouth to mouth is to fill it from one end to the other. All of these are spatial and physical uses, kept apart here from a person's mouth and from speech.

In a set of very common phrases the word no longer names a mouth at all. Attached to a small linking word, it becomes a way of matching one thing to another, and English usually drops the word "mouth" entirely.

One branch measures: something is done in proportion to a number, a length of time, or what a person can afford. The picture behind it is a mouth that names the amount, and the action then lines up with what was named.

The other branch points to authority: an action taken by the mouth of someone is done on their order, and a matter settled by the mouth of two witnesses stands on their testimony. Here the mouth stands for the word that carries weight, whether a ruler's command or a witness's sworn statement.

In a few places the word names a measured share of something divided up. The clearest is the phrase "a mouth of two", the double portion the firstborn son inherits and the same measure Elisha asks of Elijah's spirit. A related use speaks of parts being cut off and a portion left standing.

The tie to the other meanings is the idea of a measured amount, the same logic that drives the phrase for measuring one thing against another. Here, though, the word names the share itself rather than the standard it is measured against, so it reads as a portion or so many parts. It is a small and specialized use, and exactly how much the idiom counts is debated (see below).

In 1 Samuel 13:21, this is not the usual word for "mouth". It names a pim, an Iron Age weight used to state the blacksmiths' charge for sharpening tools. Inscribed weights identify its value as about two-thirds of a shekel.