:core: n. Main storage or RAM. Dates from the days of
ferrite-core memory; now archaic as techspeak most places outside
IBM, but also still used in the UNIX community and by old-time
hackers or those who would sound like them. Some derived idioms
are quite current; `in core', for example, means `in memory'
(as opposed to `on disk'), and both {core dump} and the `core
image' or `core file' produced by one are terms in favor. Some
varieties of Commonwealth hackish prefer {store}.
-- The AI Hackers Dictionary
fandango on core: [UNIX/C hackers, from the Mexican dance] n.
In C, a wild pointer that runs out of bounds, causing a {core
dump}, or corrupts the `malloc(3)' {arena} in such a way as
to cause mysterious failures later on, is sometimes said to have
`done a fandango on core'....