Symbols I don't really wish to state the obvious here such as, what suns and moons are symbols of. Instead, what I'm going to do is let you know some archeological, historical, and rarely remembered meanings of a number of symbols. Hearts are not only symbols of love and friendship, but also, lusty sex. The same applies to the buttocks area when you bend over. I can't decide whom I feel sorry for - the overwhelmed female snake or all the male snakes that don't make it to the finish line.
Knots are fertility symbols.
Circles, like knots and snakes, represent infinity and immortality. Circles are easy to see as fertility symbols - the warmth of a sun shining and the crescent to full phases of a waxing moon meant things would grow and flourish. However, the sun and the moon never disappeared from the sky forever. They always returned after clouds, the night, the day, a storm, etc. It is why fertility concepts are so closely related to immortality and infinity concepts such as, reincarnation.