nisi Dominus frustra

if not the Lord, [it is] in vain

Notes

That is, "everything is in vain without God". Summarized from Psalm 127, "nisi Dominus aedificaverit domum in vanum laboraverunt qui aedificant eam nisi Dominus custodierit civitatem frustra vigilavit qui custodit" (unless the Lord builds the house, they work on a useless thing who build it; unless the Lord guards the community, he keeps watch in vain who guards it). The motto of Edinburgh.

Words

nisi – except, if not, unless
frustra – in vain, mistakenly, wantonly, without reason
domina – lady, mistress
frustro – deprive, disappoint, dupe, to deceive, to defraud, trick