Recommend keyword research tool for Pinterest....

I have 8 months old account on Pinterest and I was posting 3 pins a day but I gave up as I was not getting huge traffic. After 6 months I found that my account is getting some traffic and I have 9 followers as I created 2 boards one in Quotation niche and other is in Digital marketing. My question is that how you guys find low competition and high search volume keywords for pinterest pins? What are your strategies while choosing the terms?