Man pages matching name curlmopt_max_host_connections in section 3:

CURLMOPT_MAX_HOST_CONNECTIONS.3.en	debian 10 / libcurl4-doc
CURLMOPT_MAX_HOST_CONNECTIONS.3.en	debian 11 / libcurl4-doc
CURLMOPT_MAX_HOST_CONNECTIONS.3.en	debian 12 / libcurl4-doc