I-M,K-G, et al, sorry ,corrected the second one;you can check WIKI,of course; developed,says D-S, by the RLM at Rechlin,(Farnborough `s equivalent in Germany) in WW2, when testing captured a/c,as a simplistic way of measuring T/o perf; weigh a/c,calculate wing area,therefore loading,use a conservative Cl,and calculate approximate Vs;use Vs x1.1 as Vlo,measure out strip,open up and go..!!Once airborne you can then verify/adjust speeds accordingly...
Obviously a little more to it,but that`s about it.
The `other 50%` will not necessarily ensure you stop in time,but you can hope that the brakes have better decel than the accel. You can of course do the calcs.yourself,by timing to a fixed speed,at varying weights/different surfaces/different power and check against a POH/or make your own...I would advise a suitable long runway to start...It`s how the performance charts were developed; I did see somewhere recently,on Pp.or elsewhere,a `howgozit` accelerometer,which may have been used on earlier big jets,to show if you had the correct accel..if not..Stop...
D-S book `Flying Qualities and Flight Testing the Aeroplane` isbn 0-632-05056-X..Sect.4,p247