Meaning
A blast from the past is used to express nostalgia. Usually, we say it when we hear a song that we forgot about. However, it can also be used to talk about something that reminds you of when you were young.
Example: I played tag with my friends. It was a blast from the past.
Origin
A blast from the past is often used in regards to music because that is where it comes from. Radio DJs started using this phrase in the 1960s. We aren’t sure who first used the term. It may have been Jerry Blavet, Jocko, or Murray the K. Those DJs used a lot of rhymes in their work. The phrase might have caught on because it rhymes.
See Also: Ahead of one's time, Spring chicken, Just like riding a bike
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Reference:
https://www.phrases.org.uk/meanings/66500.html
https://writingexplained.org/idiom-dictionary/blast-from-the-past
https://rollsoffthetongue.tumblr.com/post/155538884050/blast-from-the-past-origin-mid-20th-century