It is a play off the purposeful misspelling of "HOLD" to "HODL" seen commonly across the crypto space

the origins of HODL date back to a viral reddit post about one's frustrations with crypto volatility, leading him to say that he will just HODL all his BTC

others have also said that HODL stands for "Hold On for Dear Life"

So HOLD:HODL::BUILD:BUIDL

hope this helps =D