I want to know what questions are most asked/queried in Google that begin with/contain: "What X do I wear with Y?" where X might be shoes and Y might be green shorts. Is there any way I can find this out?
That doesn't give you search volumes nor does it complete partial phrases because there's not enough search volume to display related terms. It shows change in searches from a maximum point (=100) so like an index - this isn't what I'm after at all.
"Google keyword tool" gives you details about how many exact or broad searches are being made per month in a specific country or globally where as "Google Trends" shows which city or country searches a particular keyword the most and when.