Er and Hello

Er noun - A trivalent metallic element of the rare earth group; occurs with yttrium.

Hello and er are semantically related in emphatic exclamation topic. In some cases you can use "Hello" instead a noun "Er".

Hello noun - An expression of goodwill upon meeting.

Er and hello are semantically related in boo topic. You can use "Er" instead a noun "Hello", if it concerns topics such as wow.