I believe your parent has it right: cast in this case means thrown or tossed. "to cause to move or send forth by throwing cast a fishing lure cast dice", sense

I believe your parent has it right: cast in this case means thrown or tossed. "to cause to move or send forth by throwing cast a fishing lure cast dice", sense 1a here: https://www.merriam-webster.com/dictionary/cast https://www.merriam-webster.com/dictionary/cast - https://en.wiktionary.org/wiki/the_die_is_cast https://en.wiktionary.org/wiki/the_die_is_cast - https://idioms.thefreedictionary.com/die+is+cast https://idioms.thefreedictionary.com/die+is+cast