Why does echo $-1 output this?

Question

Can someone explain me what is happening here? What does the output means?

:$ echo $-3
himBH3
:$ echo $-2
himBH2
:$ echo $-1
himBH1

Thanks.

Answer 1

$- is a variable that contains the currently active shell options.

-

(A hyphen.) Expands to the current option flags as specified upon invocation, by the set builtin command, or those set by the shell itself (such as the -i option).

Your command is evaluating to the value of - then a number.