What’s a concertina phrase?

A concertina phrase, phrase Z, is a phrase in English which will be fashioned from splicing collectively two different English phrases, phrase X and phrase Y, such that the letters of phrase X kind the odd numbered letters of phrase Z, and phrase Y, the even ones.

It could be easiest to elucidate with a easy instance:

The phrases FRIENDS is a concertina phrase as a result of it may be fashioned from the phrases:

    1234567
    F I N S
and  R E D

While the prize (‘what prize’ I hear you ask) goes to the longest phrase, bonus factors (‘what bonus factors’) are on supply for attention-grabbing solutions – as an illustration, the place phrases x, y, and z make a believable phrase, or the place the subwords resonate with the that means of the superword.

Rosie F advises that this type of development is definitely known as an alternade q.f. https://en.wikipedia.org/wiki/Alternade (though I like my time period higher).