"Melt up"?

I was struck yesterday by the term Melt-Up in a story about the stock market: "Tech Melt-Up Drives $3.5T Nasdaq 100 Gain in Four Days", Bloomberg 8/5/2026:

A dramatic turnaround in technology stocks has powered a $3.5 trillion increase in the Nasdaq 100’s market capitalization in just four days, driven by strong earnings that have emboldened investors about the AI outlook. The tech benchmark has jumped 9.3% over this period, its sharpest rally since April 2025.

I don't recall having seen "melt up" before, although it's obviously the rising equivalent of a falling "melt down", in the sense that Wiktionary glosses as "to collapse or fail utterly", as a figurative extension of "to lose structure by being heated to a molten state". And stock market episodes described with the phrase "melt up" have been around long enough in financial commentary that Wiktionary has an entry for the verbal form, with the gloss "Of the price of a security, to increase to an unexpected degree."

It's easy to find older examples, e.g. from Marketwatch in 2014:

It suggests that we could see all of 2013's epic melt-up rally reversed by April with the selling intensifying in March.

But independent of the application to market prices, I was surprised to learn from the OED that people have long considered "melting up" as the right way to describe (some cases of) heating things to a molten state. For example:

Thomas Jefferson 1786 Let them melt up their eagles & add the mass to the distributable fund that their descendants may have no temptation to hang them in their button holes.
Mark Twain 1872 We melted it up and made a solid brick of it by pouring it into an iron brick-mould.

I should have anticipated that, since the semantics of phrasal verbs is at best quasi-compositional. The spatial-direction metaphor for increasing and decreasing prices is well fixed as rising/falling and up/down, so the meaning of market melt-ups and melt-downs are similarly clear, though the metaphorical connections to temperature and physical state are tangled or worse. And maybe those tangles explain why psychological "melt down" is common, but (as far as I know) the analogous psychological "melt up" has yet to be observed.