About ten years ago I had a camping holiday in Portugal. We were often the only foreigners on the camping sites and the Portugese were always very friendly... in the mornings they would always greet us with a "bom dia!" which of course means "good day".
The thing was though, the way they pronounce it down there you don't hear the "b" and they kind of swallow the "m" in their noses so it sounded as if they were all going round saying, "oh dear, oh dear" to us.
And strangely, after that-thing-yesterday-which-I-am-not-going-to-mention just now, it seems very appropriate that the Portugese should be saying, "good day, GOOD DAY!" and that to us English it should sound like, "oh dear, oh dear".