tail off (also tail away British English) phrasal verb (see also tail)

1. to become gradually less, smaller etc, and often stop or disappear completely:
Profits tailed off towards the end of the year.

2. written if someone’s voice tails off, it becomes quieter and then stops:
‘I didn’t mean ...’ Her voice tailed off in embarrassment.

[TahlilGaran] Dictionary of Contemporary English ▲

tail off
to gradually lessen.
Sales of new cars always tail off when people are worried about losing their jobs.

[TahlilGaran] English Idioms Dictionary ▲