You won’t find cascave in any dictionary, since the
word was coined by the children of our correspondent. Cascave fits (or
should we say falls) into the linguistic category known as family
words.

According to word-collector Paul Dickson, a family word
is coined by (and used almost exclusively within) a family. Family words
usually aren’t written down, and only rarely do they become established in the
general lexicon. One exception is googol, the name for the number one
followed by 100 zeroes. That word comes from the nine year old nephew of
American mathematician Edward Kasner.

Family words usually fill a specific need. The blend word
milkstache is shorthand for a milk mustache. The acronym F.H.B. (for
Family Hold Back!) is an unobtrusive way to enjoin family members to
restrain themselves in front of guests when food is in short supply. The
onomatopoeic nicknocks names automobile turn signals.

Occasionally, adults discover that what they consider family
words, the rest of the world considers part of the general vocabulary. Such is
the case with the terms mudroom, church key, and pie-eyed,
all of which were reported to Dickson as family coinages.