He saw her frequently after age 18 , often exchanging greetings in the street , but he never knew her wellâ '' he effectively set the example for the so-called `` courtly love '' . He saw her frequently after age 18 , often exchanging greetings in the street , but he never knew her well ; he effectively set the example for so-called courtly love , a phenomenon developed in French and Occitan poetry of the preceding centuries .