c.1600, from Italian zero, from Medieval Latin zephirum, from Arabic sifr "cipher," translation of Sanskrit sunya-m "empty place, desert, naught" (see cipher (n.)). A brief history of the invention of "zero" can be found here. Meaning "worthless person" is recorded from 1813. Zero tolerance first recorded 1972, originally U.S. political language.
in zero in, 1944, from zero (n.); the image is from instrument adjustments.
zero ze·ro (zēr'ō, zē'rō)
n. pl. ze·ros or ze·roes
The numerical symbol 0, indicating the absence of quantity or mass.
The temperature indicated by the numeral 0 on a thermometer.
To aim at or concentrate on a specific person, thing, etc; single out: We're trying to zero in on the problem
[1944+; fr the zeroing of the sights of a rifle, that is, adjusting the sights so that the round hits the exact point aimed at and the shooter needs to make no, or zero, estimated correction in aiming]
A truly insignificant person: That zero will never get her to go to the dance