what do the us, idh, idv stand for in the MCMCglmm in R

Question

I am having hard time remembering the meaning of the us, idh, and idv functions in the MCMCglmm. I understand that these are the functions taking random variance-covariance structure into account, but are they abbreviations of some words in English? It would be helpful to know it to remember them and their underlying meaning. Thank you very much.

Answer 1

In the MCMCglmm package in R, we have, from page 19 of the documentation:

idv fits a constant variance across all components in formula. Both idh and us fit different variances across each component in formula, but us will also fit the covariances.

As far as I know, none of idh, idv, or us are related to any particular statistical terms. In fact, I cannot find any references to these terms outside of the MCMCglmm package.