People talk about a love affair as a romance, and think of a romantic gesture as an expression of modern love. Romantic poetry is pretty much equated with love poetry and for the purpose of Valentine's Day and sentimental occasions this is probably true and adequate - yet ‘romantic’ has a much looser meaning. ‘Romantic’ really just means something related to fiction, an ideal, story-like situation - both the French and German word for novel is ‘roman’. Hence the expression ‘romantic notion’ doesn't actually refer to an idea based on love – it is used in the original sense.
However, it is easy to see how the period of Romantic poetry, which began in the eleventh century and wasn't necessarily about sexual love, gave rise to the modern notion of romantic poetry = love poetry that we use in wedding ceremonies today. Romantic poetry was performed by the troubadours as they travelled from court to court in southern France, celebrating courtly love and adventure. ‘Romance’ was the name given to a story in one of the romance languages, notably French. Romances told fictitious tales of chivalry in which imagination was unrestricted and ideals were striven for and lauded – which was far from the realism of preceding literature. ‘Romance’ came to mean any unreal, improbable or impossible story.
For centuries then ‘romantic’ meant ‘like the old romances’ : fantastic stories of knights, dragons, magicians - in an incredible, fanciful, even absurd world. Then the word evolved to mean pleasing to the imagination, attractive, alluring and captivating. Towards the end of the eighteenth century it began to be used for anything which aroused feelings of awe or wonder at unusual or unearthly beauty. Later it came to take on the meanings ‘magic’, ‘suggestive’ or ‘nostalgic’. Finally it came to mean something you can't describe in exact terms, something infinitely desirable to the heart, something that draws the senses inexplicably, something we cannot resist. This ‘romantic’ attraction that demands romantic, senseless gestures to impress your loved one!