This chapter gives a short account of the mathematical studies of helicity and Schraubensinn (German) from 1937 to 1969. Those works were done by famous mathematicians, applied mathematicians, and physicists, including Poisson, Maxwell, Hamel, Lee, Elsasser, Woltjer, Moreau, Betchov, Steenbeck, Krause, and Moffatt. Helicity is important in all scientific and technological/engineering disciplines.