Where did this phrase originate from? What does this refer to? I know what it means, but does it originally mean walking off a ship on a sword along the edge as opposed to the flat?
Learn English – the origin of the phrase “on edge”
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Best Answer
There are multiple senses of the phrase "on edge," so to some extent it depends on what meaning you're referring to, but most senses appear to derive from the longer phrase set (a person's) teeth on edge.
According to OED, this is the earliest sense. First literally, meaning ‘to cause an unpleasant tingling in the teeth’, and then figuratively in the senses that will be outlined below. Uses in the literal sense are attested from 1382.
What exactly is meant by the earliest, literal uses of setting teeth on edge is a reasonable question. According to a note in OED:
In other words, the earliest sense comes from a Latin Bible translation that might have meant to numb the teeth.
On edge in the first figurative sense, meaning full of eagerness, is attested from 1580:
An early example of this sense:
More recently, attested since 1872, "on edge" can mean to be excited or irritable.
This use is frequent in contemporary English, so it's likely that this is the sense you are asking about. As you can see, it traces back through various meanings over time.