1
general::
Gradually become extinct, as in As technology advances, and Western culture spreads, many folk traditions are dying out. [Mid-1800s]
American Heritage Idioms
2
general::
Phrase(s): die out
1. Lit. [for a species or family] to perish totally because of the failure to produce offspring. • I am the last one in the family, so I guess our line will die out with me. • The owls might die out if you ruin their nesting area. 2. Fig. [for an idea, practice, style, etc.] to fade away through time. • That way of doing things died out a long time ago. • It died out like the horse and buggy.
McGrawhill's American Idioms And Phrasal Verbs