[FOM] A historical question about notation

[T.Forster at dpmms.cam.ac.uk]

Over lunch today with one of the members of this list, the question of the 
notation for the empty set came up. I am wondering if listmembers can 
confirm the following allegations which i find floating around inside my 
head..

1   The capital $\Lambda$ notation for the empty set (used by Russell and 
    Quine) is a capital `L' connoting German `leer';

2   The `v' for disjunction comes from Latin `vel' meaning `or';

3   `$\cup$' for set union derives from vel;  

4 `$\cap$' derives from `$\cup$' and `$\wedge$' analogously from `$\vee$' -
    turning symbols upside-down connotes duality.

5   `$V$' for the universe is an upside-down `$\Lambda$'.

I'm pretty sure about (2) but not at all confident about some of the 
others.