½ρV² is simply the result of first order integration of ρV with respect to V...
Study the derivation of Bernoulli's result, considering incompressible fluids and the continuity equation for inviscid fluid flow and you'll find that dp=-ρVdv. Simple integration will then yield p= - ½ρV² + const, meaning that the sum of static and dynamic pressure remains constant for the steady flow of an ideal fluid. Since p is static pressure (normally written as S), ½ρV² can only be the dynamic pressure, normally written as Q. Thus S+Q=const!
If you don't understand the level of schoolboy calculus which I was taught at the age of 15, then just accept that L=CL½ρV²S....