The keypoolrefill RPC fills the cache of unused pre-generated keys (the keypool).
keypoolrefill ( newsize )
*bitcoin-cli help keypoolrefill
keypoolrefill ( newsize ) Fills the keypool. Arguments 1. newsize (numeric, optional, default=100) The new keypool size Examples: > bitcoin-cli keypoolrefill > curl --user myusername --data-binary '{"jsonrpc": "1.0", "id":"curltest", "method": "keypoolrefill", "params": [] }' -H 'content-type: text/plain;' http://127.0.0.1:8332/