when computing profile confidence intervals using confint(m1) where m1 is a glmer() model there is a term ( or a few ) at the top which are labelled .sig01, .sig02, I can't find any documentation which explains what these mean though.
You probably didn't find the documentation for the 'merMod' class method of confint. In ?lme4::confint.merMod the following can be read at the parameters:
oldNames: (logical) use old-style names for variance-covariance parameters, e.g.".sig01", rather than newer (more informative) names such as"sd_(Intercept)|Subject"? (See signames argument to profile).
The default option for oldNames is TRUE. Setting it to FALSE will give you a clearer output.
Example
library(lme4)
(gm1 <- glmer(cbind(incidence, size - incidence) ~ period + (1 | herd),
data = cbpp, family = binomial))
confint(gm1, oldNames=FALSE)
# 2.5 % 97.5 %
# sd_(Intercept)|herd 0.3460732 1.0999743
# (Intercept) -1.9012119 -0.9477540
# period2 -1.6167830 -0.4077632
# period3 -1.8010241 -0.5115362
# period4 -2.5007502 -0.8007554