Pif! Paf! Which is the elephant and which is the mouse? There's no real link between the sound of most words and what they mean (with the exception of onomatopoeias such as 'buzz'), but that doesn't prevent people from making sound associations. Writers can use this tendency to advantage, especially in poetry. You can use sound association to create a mood, or to subvert it. If you've used 'm' to create associations with 'mother', 'milk' and 'mild', subsequently using 'murder', 'mayhem' or 'mischief' has extra shock value.
As Alexander Pope puts it in his 'An Essay on Criticism' (lines 362-374):

True ease in writing comes from art, not chance,
As those move easiest who have learn'd to dance.
'Tis not enough no harshness gives offence,
The sound must seem an echo to the sense...

Back to the elephant and the mouse. Here's a clue: one's small, quick and light, the other is big, heavy and slow. What do they sound like to you?